Because it makes the peen look smaller and you get less depth penetration and cant feel as large with a woman who has large thighs. Unless you are Gronkowski or Thor size how are you supposed to feel giant to a 5"6 woman with curves and big butt and thighs?
My peen is long but not thick. I feel intimidated by big thighs and thick booty as it means I get less depth. The curves and stuff gets in the way and my peen looks less big. Also, while not a manlet I am thinner side and not so muscular. Bigger women I feel less powerful around and they are litterally heavier to move around.
But on a girls butt like this???
Easy manhandling and no resistance.
This below intimidates me. Subconsiously this below is why men opposed to big butts are opposed. Its because their peens and manilness in general is less around bigger women.