The inability to leave one's ego at the door, resulting in sacrificing form for poundage.
IMO, most people would be better off not squatting with a weight that they couldn't get onto their backs if they didn't have a squat rack.
I don't think so. Well, its not the case for me anyway. You just have to look at how people squat in every day life. Almost everyone comes up off their heels, rounds their back, and doesn't achieve enough flexion in their hips and ankles.
I've tried stretching, adjusting my form, everything I can think of for over a decade now, and I still haven't made much, if any progress. I think a lot of people are simply unable to do the movement with any degree of resistance, like me.