What is the purpose?

I dislike crossfit kids. I give Crossfit some leeway because I've seen some people get good results when the technique and programming are correct. When they start doing this stuff to kids who trust them I run into problems.
There was a video a while back of another kid doing the exact same thing the kid in this video does, but facing a wall. He dumps the weight and misses ramming his head into the wall by about an inch.



The point of this isn't to pick on Crossfit, but to pose a question. Why are we doing the things we are doing? Even in so called 'randomized training' the exercise selection should make sense. Unless you're training to be a powerlifter what exactly is the purpose of doing max load barbell back squats? Now, I've attended Louie's seminar and heard him talk about using powerlifts for athletes. The key there is 'athletes', and high level ones at that. Louie also doesn't only do powerlifts with them.
The question is WHY does the general population need to do heavy barbell back squats? Or even barbell deadlifts? This isn't to say the movement is bad. All of my clients squat and deadlift, but they do it with kettlebells, or sandbags, or sticks. What is going on with a barbell back squat that isn't occurring during a front squat, or a kettlebell goblet squat? Some things to be sure, but are they necessary for the man or woman on the street. I regularly see trainers loading up female clients with heavy barbells on their backs. Why?
Aside from the question of 'why' do the exercise at all, what about dysfunction? A barbell back squat requires flexibility, mobility, and stability to a degree most people do not have. So why load them up to do an exercise that even if they want to do it, they flat out can't?