I think it's interesting to compare the House Elves of Harry Potter to more traditional serving pixies, brownies and whatnot

Brownies. House Elves are almost certainly based on Brownies, including the method of getting rid of them being to give them clothes. There are other househould spirits, but Brownies would have helped in hearth and kitchen and being rewarded with bowls of milk.

Somehow the Wizarding World seems to have domesticated Brownies so that they *have* to help, and can't take the normal Brownie revenge for being insulted -- souring the milk, ruining the cheese, and generally creating havoc in the house.