I'm a female bottom watcher, as a female, I think a small petite well shaped bum is much more attractive than a large one. Some women have perfect bottoms that turn heads, I'm usually thinking whilst watching, yep, once upon a time. Or I may say, is mine the same size as hers or smaller. Own up, anyone else do that, ladies?
"Maybe the media has made us slim down" Probably. There was a time (circa 1950 something) when an hour glass figure was the ideal. Small waist (never had kids before) and wider hips (for childbearing)
Whilst tastes can change I don't see this as an explanation.
As a general rule minimal bottoms are what females prefer, thus the worry about whether their bum looks big in whatever they are wearing. I get the impression many tend to prefer the 'adolescent boy look' from the back view. Whereas I think most males like a bit of squeezable curvature as long as it's not spread nor droopy (nor false/exaggerated looking) within reason. After all, who really prefers a bony bum ?
Black men like big bums and black culture is prominent now. I remember being in Nigeria with a (white) colleague. She said "Black men tend to go for me because they like my African ***"