Bit of a sideways thought, but I wonder if the amount of (illegal) cosmetic procedures on animals (such as ear cropping) has increased since cosmetic surgery in humans has started to become more common place? There is a certain demographic who see procedures such as fillers, boob jobs, botox etc as routine 'self improvement' tasks, and on SM they seem to be the demographic that now often (but not always) owns dogs with cropped ears.
Mind you, cosmetic procedures on animals have been carried out for centuries (ear cropping in dogs and horses, tail docking in dogs and horses, tail nicking in horses etc) so it's probably more a case of nothing changing, which is sad as humans believe themselves capable of education and improvement as a species.
To be clear, I don't think any cosmetic surgery should be carried out on animals (or humans who can't give informed consent, such as children), and it is beyond me why someone would want to.
It's a very interesting point! But as you say it's been done for a long time, pre-dating the fads for/availability of cosmetic surgery.
Breeds like Doberman and other pinschers, Boxers, Beaucerons, Rottweilers etc were routinely cropped and docked on the continent when I was growing up and it was big in the USA too. Even Great Danes were cropped.