I’m not a dog owner, but aren’t flappy ears and a wagging tail what make a dog a dog?
Anyway, just a wild guess on my part, but dobermans are often used as guard dogs, so removing most of their ears and their tails leaves a potential assailant with less to grab hold of. Still, methinks if the people-who-be want a dog with such traits, they should selectively breed those traits instead of mutilating the dogs.