Oh, 90% of people in the gym at any particular time are doing an exercise with horrible form. I try to help anyone that will listen, but a lot of guys have egos and don't want to hear it..So I continue to let them quarter squat 315 when they should be doing 135.
Also, most people's hamstrings,lower back, and glutes are grossly underdeveloped so they lean on their quads more than they should when squatting. Without having the proper development its really hard to sit back as far as you should and get depth.