I grew up on a farm and I've wondered the same thing. I remember seeing a TV show a few years ago where a van load of teenagers hit a raccoon, and then debated whether to spend their money on the concert they were headed to or on a vet for the raccoon. I think they picked the raccoon. I couldn't understand why they didn't just put the poor thing out of its misery and go on, and also why they weren't afraid of it biting them.
Because they didn't have good sharp knife in the car to cut its throat, and because every city liberal knows injured wild animals never bite, just look at you soulfully and beg for help.