Why do pirates have hooks on there hands?

Answer 1

Hooks and peg legs have been commonly-used prostheses throughout history, and are in fact still used today. They aren't limited to use by pirates, though popular image associates them with pirates.

If a pirate lost a hand, a hook could be easily found on a ship. However, there wasn't a doctor present--the chef performed the surgery.

That being said, it wasn't terribly common.

Answer 2

Hooks have been a common prosthetic answer to a lost hand for centuries--it's not just limited to pirates.

That being said, it wasn't common, and I sincerely doubt any pirate amputated his or her hand just to have a hook.

Answer 3

Being a pirate was a quite violent life, and injuries from fighting were common. If someone was unlucky enough to lose a hand due to a sword cut for instance, but lucky enough to survive it, they could use a hook as a crude form of prosthetic limb.