Most reputable AKC breeders follow the breed requirements: docking and cropping for a proper Doberman. My opinion only: uncropped Dobes just look like another hound dog...crops look so much better and have no ear infections! So consider that with floppy eared dogs they tend to have more ear infections.
I think sometimes we humans just "parrot" things we've heard, without really knowing the facts or if science bears out our opinions.
It has been thoroughly debunked that natural ears are more prone to ear infection--in fact, the number one reason vets cite (and studies conclude) for ear infections is allergic/immune issues.
As for saying natural Dobermans "look like another hound dog," that is insulting both to owners of uncropped dogs, and to yourself--because if ears are the only distinction your eye is able to find, between a hound and a Doberman, well, you don't have much of an eye, and certainly do not know your breeds.
Edit to add: My erect-ear American Hairless Terrier has had ear infections twice. With her breed and her ear set, can't get much more air going in that ear canal
