it just like going to a studio and hiring a steel player and a drummer, and a piano player...etc.... Since I wouldn't have too much say over how they would play the parts..... what's the difference?
I think you make a great point about recorded music. To me a recording is different from a live performance because all recordings are heavily engineered, mixed, mastered, recorded and re-recorded, use musical wizards, patch together various takes to get the best one, etc.
So BIAB is just the poor man's small army of excellent session musicians! The only drawbacks I'd see to using BIAB on recordings is 1) it becomes difficult for me to add my own instrumentation because honestly I am not as good as my band in a box and 2)
some of the tracks can start to sound a little similar (because of the few I really love to use)!