Dwarves have massive asses, they just don't usually wear the kind of clothes that accentuate it (also, they're kind of hard to see for tall races)! I mean seriously, they're supposed to be stout and have a lot of stamina for working in mines and the like, you can't really have that kind of build with a flat ass.

With how wide dwarves are, their asses must naturally be huge. It's just that you're too hightist to notice.

That is why I love fantasy stories. They really show how gender and norms are social constructs. Its fun to play with

I aspire to that goblin androgony dream