Why don't wizards use a greater variety of spells when duelling?

Question

In the Harry Potter books and movies, only a few different spells are used, even though there are thousands of extremely useful spells that are never even mentioned in the books. What is the reason that wizards or witches only cast a few spells, such as Stupefy?

In the Battle of Hogwarts it appeared that both sides used mainly stunning spells despite the fact that there are many more effective forms of battle magic that are taught at Hogwarts.

Is there a reason that a large amount of spells seem to be forgotten by wizards?

Answer 1

First off, there aren't thousands of spells. There's less than a hundred mentioned in the entire Potterverse, 99% of which are utterly useless in a duelling situation. Casting Tergeo might be useful when cleaning a mess, but it's pointless when someone is trying to kill you.

Offensive spells make up a vanishingly small fraction of all spells. The following is the entire list of (known) spells that can be used in an offensive mode.

Avada Kedavra, Confringo, Confundus, Conjunctivitis, Crucio, Deprimo, Expelliarmus, Expulso, Furnunculus, Immobulus, Incarcerous, Incendio, Langlock, Levicorpus, Locomotor Mortis, Petrificus Totalus, Reducto, Sectumsempra, Stupefy.

and of those, it's really only Avada Kedavra, Confringo, Crucio and Sectumsempra that are truly damaging. All the others simply move people around, knock them back, temporarily blind, bind or disarm them or cause mild discomfort. That's not to say that other spells can't be used offensively (note the effectiveness of Molly's Reducto spell) but just that they're not the most obvious choice.

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On top of that, Wizards and Witches (at least those in the UK) are taught duelling at Hogwarts so there's a strong confirmation bias that because they all learned the same way in the same place, they're likely to use the same techniques.

Answer 2

The first is that almost all spells require effectively the same amount of effort - Will, focus, line of sight, a wand, a word (or two). In a duel there's only one objective, and that is to have stop the opponent. In this case alone, there's not much reason to switch between spells, because as soon as one hits, you win.

Second, in stressful situations, there's a quote by Archilochus that is repeated from children's martial arts dojos to the highest levels of military — 'We don't rise to the level of our expectations, we fall to the level of our training.' The characters seldom have a chance to sit and think about which spell they're going to use - only those that have been wizards the longest seem to have large variations in the spells they use, and the series is focused on teens who don't have a huge "spellbook" per se to begin with. Even in the Dueling club they set up themselves, Dumbledore's Army doesn't train their participants to be creative, they teach them how to be effective. Snape uses Sectumsempra in lieu of others as it's his personally created curse, and uses it as a signature, to the point where Lupin could take a single look at George's (lack of) ear, and say "This is Snape's work".

Lastly, the spell that characters choose has a certain metanarrative built in. Voldy uses Avada Kedavra on anything, solidifying his character as one who kills indiscriminately. Potter, the OotP & co almost exculsively use either Stupefy or Expelliarmus (Stun or Disarm, respectively), because they respect the life of the target, even if that target is trying to actively kill them. They could use other spells that have the same basic effect - say, petrificus totalus - but it doesn't give any larger benefit than Stupefy, but takes twice as long to say. Snape uses his Slashing curse that is viewed in a gray area - the "good guys" see it as nonlethal, while the "bad guys" view it as cruel enough. In an actual battle, there's no real benefit to switching spells, save adding larger scale environmental effects (Reducto starting an avalanche in the hall, Voldy Vs Dumbledore dueling in the MoM, Patronuses to counter dementor attacks, et cetera).

Answer 3

Not every wizard or witch is going to be at the level of someone like Dumbledore where they can do things like bring statues to life and have them fight a for while controlling huge volumes of eater or making a gigantic inferno. The Harry Potter franchise is very clear that those levels of magic and anything that might seem exotic is extremely high level spell casting that the average with or wizard isn't going to be capable of. Most magic we see isn't for combat, anyway.

Also, one good Stunning spell can be the opening door to either further incapacitate, or do whatever else to one's target, so arguably, any of that fancy stuff may not even be necessary.

Answer 4

There are not a lot of combative spells in Harry Potter.

For example, Silencio. Yes, Hermione did use this spell against Dolohov but she still got incapitated. Why? Because the effects of the spell can be countered by a simple non-verbal spell though this spell might prove useful in a duel against a wizard incapable of non-verbal magic. But why use that spell when you have Stupefy and Pertrificus Totalus? If you are hit by those spells, you are instantly out of the duel and can only come back in when the effects wore off (which usually takes hours and duel would be over) or one of your allies perform a counter-spell. However, more powerful wizards like McGonagall can use her environment to her advantage like making the fire from a torch fly at the opponent. A less powerful wizard would be certainly be defeated and only a powerful wizard like Snape can counter it. Those spells however are immensely difficult and many cannot perform it so just stick to a Stunning Charm.