When I have bought my last three cars from a franchised dealership, in all cases I had to produce my driving licence during the time of hand over. I don't know if this has anything to do with the fact that the cars were automatically subject to 7 days insurance (although I have always obtained a cover note from my own insurers before collection day). Or could it be to protect the dealership of any come back if the driver was stopped and found to not have a proper driving licence.
These types of queries usually occur because, or so it appears, the buyer MUST get his/her hands on it NOW. If the car is held under a deposit, then waiting to ensure that all documentation is in order must surely be the most sensible approach.