What would have happened if Gladys Knight had fired one of the Pips? Or if Booker had had a falling out with one of the MGs?
I think Gladys would have found another way to get to Georgia.
The problem with being a sideman is that you make it (or not) at the whim of the front man. In exchange for the intellectual comfort of being handed a chart, you give up control and your ability to lead.
Most of all, instead of having a relationship with the audience, you merely have a relationship with the front man.