Why weren't more Death Eaters kissed by a dementor?

Question

Why didn't Dumbledore and the Ministry have most, if not all of the Death Eaters caught kissed by a Dementor, especially ones like Bellatrix?

Answer 1

First: As the Dementor's Kiss is widely regarded as a fate worse than death, it would not be a sentence handed down often -- if at all -- in a society that is generally anti-capital punishment.

By the Ministry, generally: Though we don't know much about sentencing guidelines for magical crimes, one of the things we do know is that even the three Unforgivable Curses carry with them "only" a sentence of life in Azkaban. The life sentence is referred to as "automatic" by Barty Crouch Jr. when he was posing as Alistair Moody, and it was for use of those curses that most of the Death Eaters were prosecuted and sentenced to Azkaban (Bellatrix and Barty Crouch Jr. for using the Cruciatus Curse on the Longbottoms, Antonin Dolohov for using Avada Kedavra on the Prewitts, and so on).

The life sentence is thus both minimum and effective maximum: the two higher sentences that we know of -- death and Dementor's Kiss -- are logically impossible to impose concurrent with life in Azkaban. It's possible, but unlikely, that whatever code of criminal justice Wizarding Britain uses allows for some wiggle room on the sentencing, the only stated exception to the life in Azkaban sentence is dropped charges for those who were forced (or could convince the Ministry they were forced) to use Unforgivable Curses.

The only two cases of the Dementor's Kiss being handed down as a sentence are against Sirius Black and Barty Crouch Jr., and was given to both only after they had escaped Akzaban. Thus, a Dementor's Kiss is likely a sentence that can be given only to those who escape Azkaban.

Dumbledore, specifically: Dumbledore, though a powerful and influential wizard, could only (potentially) influence the sentencing through his position as Chief Warlock of the Wizengamot. Since it's unclear what, exactly the position of Chief Warlock entails, it may not actually allow him any say in the sentencing of criminals. If it doesn't, Dumbledore has no judicial power. If it does, he is bound to give only those sentences allowed by law.

TL;DR: From the text, we can assume that the maximum sentence for use of an Unforgivable Curse is life in Azkaban. Captured Death Eaters after the First Wizarding War were not given the Dementor's Kiss because the law doesn't allow it.

Answer 2

It was likely considered cruel, and only used in extreme cases.

The Dementor’s Kiss is a particularly horrible fate. The Dementors suck out their victim’s soul, leaving them existing as an empty shell and destroying their soul forever.

“They call it the Dementors’ Kiss,’ said Lupin, with a slightly twisted smile. ‘It’s what Dementors do to those they wish to destroy utterly. I suppose there must be some kind of mouth under there, because they clamp their jaws upon the mouth of the victim and – and suck out his soul.’

Harry accidentally spat out a bit of Butterbeer. ‘What – they kill –?’

‘Oh, no,’ said Lupin. ‘Much worse than that. You can exist without your soul, you know, as long as your brain and heart are still working. But you’ll have no sense of self any more, no memory, no … anything. There’s no chance at all of recovery. You’ll just – exist. As an empty shell. And your soul is gone for ever … lost.”
_{^{- Harry Potter and the Prisoner of Azkaban, Chapter 12 (The Patronus)}}

Lupin implies to Harry that it’s such a horrible fate that no one, no matter who, deserves it.

“Harry sat stunned for a moment at the idea of someone having their soul sucked out through their mouth. But then he thought of Black.

‘He deserves it,’ he said suddenly.

‘You think so?’ said Lupin lightly. ‘Do you really think anyone deserves that?”
_{^{- Harry Potter and the Prisoner of Azkaban, Chapter 12 (The Patronus)}}

Dumbledore also clearly disapproves of using Dementors at all, so he’d almost certainly be staunchly against actually letting them suck out anyone’s soul.

“Let’s hear his information, I say, and throw him straight back to the Dementors.’ Dumbledore made a small noise of dissent through his long, crooked nose. ‘Ah, I was forgetting … you don’t like the Dementors, do you, Albus?’ said Moody, with a sardonic smile.

‘No,’ said Dumbledore calmly, ‘I’m afraid I don’t. I have long felt the Ministry is wrong to ally itself with such creatures.”
_{^{- Harry Potter and the Goblet of Fire, Chapter 30 (The Pensieve)}}

Because it was considered so cruel, it was unlikely to be a punishment used often, and the people against it also disapproved of it being used on Death Eaters or violent criminals. In addition, the sentence had to be approved by the jury before it could be carried out.

“I now ask the jury,’ shouted Mr Crouch, ‘to raise their hands if they believe, as I do, that these crimes deserve a life sentence in Azkaban.’ In unison, the witches and wizards along the right-hand side of the dungeon raised their hands.”
_{^{- Harry Potter and the Goblet of Fire, Chapter 30 (The Pensieve)}}

If the question regarding sentencing was ‘do they deserve to have their soul sucked out’, it’s likely at least some members of the jury would be less willing to say it’s deserved.

Punishment for comparable crimes was typically a life sentence.

Also, the punishment for the types of crimes that the Death Eaters were convicted of was typically a life sentence in Azkaban, so that would be the accepted sentence. For example, Bellatrix was convicted for torturing the Longbottoms using the Unforgivable Curses.

“Bellatrix Lestrange, convicted of the torture and permanent incapacitation of Frank and Alice Longbottom.”
_{^{- Harry Potter and the Order of the Phoenix, Chapter 25 (The Beetle at Bay)}}

The accepted punishment for using the Unforgivable Curses was likely a life sentence in Azkaban.

“Now … those three curses – Avada Kedavra, Imperius and Cruciatus – are known as the Unforgivable Curses. The use of any one of them on a fellow human being is enough to earn a life sentence in Azkaban.”
_{^{- Harry Potter and the Goblet of Fire, Chapter 14 (The Unforgivable Curses)}}

As this seems to be the accepted sentence for using the Unforgivable Curses, it would be easier to get a jury to agree to it rather than a Dementor’s Kiss. Other Death Eaters were convicted of murder, and as the punishment for using the Unforgivable Curses, which includes the Killing Curse, seems to be a life sentence, it’s likely murder also usually is given a life sentence.

“Antonin Dolohov, read the legend beneath a wizard with a long, pale, twisted face who was sneering up at Harry, convicted of the brutal murders of Gideon and Fabian Prewett.”
_{^{- Harry Potter and the Order of the Phoenix, Chapter 25 (The Beetle at Bay)}}

Since it seems to be the sentence given to comparable crimes to the ones the Death Eaters were convicted of, it’d likely be the sentence that the Death Eaters would get for their crimes as well.

Answer 3

In addition to the points made in the other answers, there may be another reason to limit the application of the dementor's kiss. If the people who currently reside in Azkaban would have instead been kissed, there would be many fewer prisoners for the dementors to guard and feed off of. If Azkaban cannot provide enough stimulation for all the dementors they will seek it elsewhere. This, of course, puts the broader (innocent) wizarding community (and Muggles as well, for that matter) at risk.

By keeping a lot of prisoners in Azkaban as opposed to just having them kissed right away, the Ministry is keeping the dementors occupied dealing with bad people, so they won't go bothering good people. Thus, the seemingly softer punishment for Death Eaters can actually be better overall for the rest of the world.

I can't prove that this is true, but it is perhaps supported by the following statement that Dumbledore makes to Fudge at the end of Gobllet of Fire:

"They will not remain loyal to you, Fudge! Voldemort can offer them much more scope for their powers and their pleasures than you can!

This seems to be indicative of the importance of giving the dementors as great a scope as possible, as otherwise they might abandon the Ministry.