Cats. Dogs are too needy for an introvert. Having to take them out for crapping, walks, and so on is a pain in the arse. The obsession with picking fights with other dogs when outside. If you leave them behind to get groceries, many go crazy, howl, and tear the place up. There is the doggy stink that requires baths, and the contest of wills to give them a bath. The fleas. The drinking out of the toilet, then wanting to lick your face. Dogs are too much like a high-maintenance gal...it's always doubtful you are actually getting as much as you're giving.