Probably the way it looks.
I guess Windows can also feel a tad clunky ergonomically since there are a couple of common tasks not smoothed out to the point of being at most two-click operations, but that’s usually because there are key commands associated with them instead, and people just don’t know they exist.
It’s either that or subjective preference. Like how OSX handles windowing and fullscreen applications. I hate it, but know a couple guys who like it.