Why do humans have finger/toenails?

Cut your fingernails way too short, then try to pick up something small. Not even with the nail part.

The hard flat back gives your flesh something to press up against when pinching. Imagine pulling a hair out of your arm with your fingers. Easy, right? Now imagine pulling a hair out of your arm with your lips.

As to why they grow and wear out and break, what the hell else should they be made of? Hands take a beating and you're better off with a material that grows back when it's worn away.

And finally, why do we have toenails? Mostly because they used to be leg hands. Your toenails actually grow about 3 times slower than fingernails, so that might be evidence of how much less useful they are to us.

Have you ever tried to scratch your balls with the tip of a hot dog?

Every other mammal has finger/toenails, most of them make very good use of it, others not that much (e.g. elephant toenails look pretty useless). Organisms don't necessarily keep inherited traits because they're useful, but because they're not very detrimental.

I recall reading something about how they give you more tactile sensation on the part opposite and let you expert more pressure but it was a little while ago, might be hearsay.

It helps with touching, percieving surfaces better if there is a hard flat support behind.

Nosepickers and ass scratchers must have an evolutionary advantage.

Because fingernails (or early versions of it) helped our cladistic ancestors survive hundreds of millions of years ago, maybe more. Maybe it helped them find food or protect themselves, or some other reason that isn't so intuitive. Certainly they helped us (as humans) to survive, but the reason we have fingernails right now is just a happy accident.

Many people in this thread or conflating what we use them for today, right now, as reasons why we have them, which isn't exactly right. Certainly they are multifunctional, especially in a modern context, but that is not the reason why we have them. All these reasons posted in this thread remind me of Psychological Evolutionists that only use logic and intuition to find reasons to why we do things the way we do, but in reality it often just happens to be that way. There is no reason for evolution other then happenstance and happy accidents.

tl;dr - We didn't evolve fingernails to pick up dropped coins, our cladistic ancestors evolved them (likely many hundreds of millions of years ago) for some reason that I don't know. Maybe to dig things up or defence. Who knows. Any way we use them today is likely just a bonus.

P.S. I don't like using evolved as a verb, as if it was a conscious undertaking. It arguably isn't, not really.

Picking up change and snorting coke.

I remember reading of a special treatment that makes them sturdy like claws. I won't mind that. A multitool made out of your fingernails can be pretty handy.

You ever get a head scratch from someone with nice long fingernails? 🤤

Same reasons monkeys have them; it helps with grabbing on to branches. The stiffness of the nail results in an increased grip strength, because the forces are blocked.