You will also find that most smallish maintenance companies don't have a pilot sitting around to do such flying. Even the big companies rarely have a slave pilot. Sometimes there is a low-time jockey, but aircraft owners don't want a bograt flying their machine, and his experience is likely such that he wouldn't know if a machine had something minor wrong.
Having done some maintenance test flying myself, I can say that it is often brain-numbingly repetitive and boring. I got out of it as quick as I could and into gunships.
