As previously mentioned, Oly shoes are elevated in the back. Weightlifters squat very deep, and the wedge helps. It can help keep the weight on your heels, especially if you have a tendency to lean forward. I am rock solid in my oly shoes. I couldn't say the same for my cross trainers. That's largely due to the lack of cushioning in the soles. As far as stability goes, I'd say the guys cleaning heavy ass weight, dropping down into a balls to the ground squat, and jerking said weight back over their heads might know a thing or two.
Now, oly shoes just to get to parallel? I don't think that's necessary at all. That's either way too much weight or a flexibility problem.