Dog breeders of Doberman dogs crop or cut the ears of the Doberman because of cosmetic reasons.
That's the only reason people cut the ears of a Doberman because it's been done for years and people want the Doberman dogs ears cropped especially if they plan to take the Doberman to dog shows to win a competition.
A Doberman with cropped ears looks much better to judges and people at dog competitions than a Doberman without cropped ears and is more likely to win the competition.
I hate when any dogs ears are cropped because I think it looks awful and it's not humane either.