system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does it hurt more to get an IV put in your hand than in the crook of your arm?

I have tiny little veins and nurses are never able to stick me in my arm, but they’re able to find better veins in my hand. Whenever I see a new doctor, I tell them to just start in my hand because the constant sticking in my arm always makes me pass out. But they always seem really hesitant, since the hand hurts more than the arm.

My question is why?
gpt
The hand has more nerve endings (sensors) because you need to feel what you're doing with your hand while doing complex tasks (typing for example).

The high density of "useful" nerves to sense touch, temperature, etc, also comes with a lot of nerves that detect pain. Arguably this serves a purpose, allowing you to detect/avoid injury while using your hands. But evolution isn't perfect, and many things that aren't clearly helpful occur as "side effects" of helpful adaptations.