"Folks who want private enterprise to develop must have some use for the thing in mind. And, I would think those reasons must be able to generate a profit.

Yours are a couple of good ones. Didn't have much interest in this thread, though, and one explanation is that there really isn't much use for a shuttle."

I think that rather than not having much use for the shuttle, it's more likely that answering this question is difficult/complicated.
In general simple terms the Shuttle could be used for space tourism- or functions which the Shuttle was designed to do- repairing deploying certain types of satellites. And/or doing science in orbit.
Could the shuttle be operated at a lower cost then what it costs NASA?
If it can't be then the Shuttle indeed has no value as a launch vehicle for any party in the private sector selling launches to private sector.
The shuttle "should" be able operated at lower costs, but the private sector needs to pay for capital costs, taxes, and make a profit.
One advantage of the private sector using the Shuttle is they wouldn't need to pay for the development costs- but then again perhaps NASA/govt will ask for this development cost to be reflected in purchase price. But rather than trying to assign some value, it's value would be better to be determined by market value.
I believe NASA should sell only one orbitor, the bidding process should be as open as possible, and terms what exactly is bidded on be "open".
Of course, what bid is considered the best value to the tax payer is another problem (fraught with all kinds political problems).