Acceptable supplemental lift for the back squat, if you're feeling beat up. I wouldn't use it for that purpose (likely to strain wrists, elbows etc cause you're doing it wrong, can't use heavy weights, hard to get volume in), but to each his own.
Might be a tool to teach yourself to put the load more on your quads during the back squat, if you feel you need to work towards that (but meh, I wouldn't try to learn it that way).
And avantgarde theory: it might help improve the overhead press since you more or less train the ohp start position but with much, much heavier weights. Same goes for push press.
Of course the front squat has all sorts of advantages over the back squat if you're training for weightlifting, but I don't know anything about that.