One reason is that I don't like narcotics, the other is that I worry that if I don't hurt a little I may think I'm more healed then I am and do something I shouldn't, like pickup the dog...
Both my wife and I are the same way. We've thrown out a bunch of unused vicodan and other painkillers over the years. She had all her wisdom teeth out and never even took an aspirin! She doesn't like feeling loopy, and I'm pretty sure without some pain to keep me in check I'll just re-hurt myself.
-Blast