I would think that yes Parselmouth is a useful skill, to only you.
Fear:
Most of the people and one of the most feared wizards ever spoke it. So if people know you speak it then they will be scared of you and possibly respect you more.
"The boy can talk to snakes, Dumbledore, and you still think he's
trustworthy?"
—Cornelius Fudge and his prejudice against Parselmouths
"Hannah, he’s a Parselmouth. Everyone knows that’s the mark of a Dark
Wizard. Have you ever heard of a decent one who could talk to snakes?
They called Slytherin himself Serpent-tongue."
—Ernie Macmillan
An unknown member of the Dark Force Defence League once stated when
asked regarding the matter by Rita Skeeter - "Personally, I would be
highly suspicious of anybody who could converse with snakes, as
serpents are often used in the worst kinds of Dark Magic, and are
historically associated with evildoers."
Skill:
Knowing it gives you another skill.
This sight gives you examples of why it is important to learn knew languages.
Also, Health from the above article.
To keep your mind healthy (from Harvey Schmidt) Learning a second
language has been proven to delay the onset of dementia.
Food
If you are in the wilderness and cannot find food and you have misplaced your wand you could summon a snake by talking to it and luring it over.
Shelter and assistance
I will get a canon quote, but remember when Voldemort was using the snakes bodies to survive after he killed Harry's parents and he needed a body so he used a snakes body.
And when he interacts with Nagini, Parseltongue probably makes it possible for him to talk to her properly and get his thoughts across.
So in the 2 above instances having communication(parseltongue) was necessary.
So besides having only selfish reasoning for it be helpful to somebody. Parselmouth is probably not useful anymore or even spoke that widely.
Most of the known speakers and people that understand it are dead or lost the power.
Voldemort
Harry
Dumbledore
So what use is a language that no one else speaks (except for the personal points above) it is worth nothing.
I would say you could learn it to speak in a language only you and your friends know, but alas no one speaks it.
So while Parselmouth is of significance to personal survival, it is only novelty in society and a scary one at that.
This has a interesting point of view and it appears that they got most of their facts right.