It is done purely for esthetics yes. However, it isn't like you slam 'em down on the ground, hold him with your knee, and start hacking away
The ears are done under general anesthetic and much care is taken to crop the ear properly. The tails are docked usually at 2-3 days old, I believe the nerves are very immature in the tail area at this point, and a good vet will remove the tail properly. There are different methods for docking, some not so humane I might add.
I believe if you research your vet and get the best possible care for the animals, then there is nothing wrong with cropping/docking.... it's the 'hacks' (forgive the pun) that try to do a job they aren't trained for and make a mess of it that give it a bad image. IMHO