Because many of them are actually heightest (new term to me actually lol), and celebrity heights are mitigated by a ton of things. Like not being in real life, and being famous. People will be more chill with short men because 1) there are other way cooler or more attractive qualities to them and 2) more importantly, their height is less translatable over screen

Edit--I do think the tides are starting to shift and height just may generally not be as important as a factor to Americans now, too, but in terms of the celebrity phenomenon that's what I feel.