Look at the low stance of sumo wrestlers - belly fat doesn't prevent them, it's all in the hip and ankle mobility.
Apparently you used to get people wearing cut-off jeans shorts while squatting in the gym, because the tension provides an extra impetus out of the bottom of the movement. A bit like a weightlifting singlet I guess. I've never seen it in person though.
Some jeans (or other tight-fitting, inflexible pants) with particular cuts might, though.
At home I can squat for about 30 seconds or so before it starts to get uncomfortable. I can do it, but haven't built up the endurance as we never use those muscles!
Also, there is no good reason to squat in an office. I'm thinking of bolting a Gameboy to the floor so you have to squat to play Tetris.
But I recently discovered that they now make stretch denim, with spandex in the knit.
It sounds like an energy drink, but Lee Extreme Motion jeans look normal but feel like running tights. And they look great, perhaps better than normal jeans because they fit better. Levi 541 and stretch 514 are good too, but have half the spandex content of the Lee jeans.
What I found was that while I can do a squat in, e.g., gym shorts, I simply can not do them with my jeans: the jeans constrain my movement substantially. And, the other thing I found, is that a bit of fat on the belly inhibits it as well.
I can't speak for everyone, but jeans and a bit of fat on the belly is sort of stereotypically "normal American" - and that can help explain it to me. Curious what sports scientists have to say here.