Well, some of you won't believe this but I have a back defect that makes it very dangerous for me to do free squats.
I've reinjured my back and been laid up every time I've tried to do free squats beyond light weight.
Sometimes when you have a permanent physical problem, you learn by trial and error that you just have to listen to your body. How many times are you going to touch a hot stove before you realize that it burns you bad every time you touch it?
Thank god I finally discovered that I am able to squat on the smith machine, so for me it is the best piece of equipment in the gym. Something about the stability. I wish I could get that on the free squat, but again, that fuckin stove is hot!