In my last job I held an auth for changing any light bulbs or fitting and removing certain role equipment on the aircraft, a police helicopter. This isn't uncommon. We were NOT allowed to do any rectification.
Yes, it was commercial expediency. The contract allowed for no resident engineering support on site and it meant a call-out of the dedicated engineer from his bed if the aircraft went tech in the small hours of the morning; he could well have been workng until late at one of the other units he supported. By giving us the auths it meant the engineer had more chance of undisturbed sleep which suited me as chief pilot because I knew he was going to be in good shape to do that 200 hour for us the next morning.
I never objected to doing an engineer's job because it was part of my contract. I received proper training to do it and let's be honest, changing most light bulbs or wire locking doesn't require an engineering qualification, just a modicum of common sense and the proper tools. We also did our own daily Check A and refuelling. My hands were dirty more often than not and I usually stank of Jet A-1 by the end of any shift. Not a large problem but no doubt there are some cack-handed pilots who didn't ought to be given a sharp knife for dinner or would object to getting stuck in... <img src="smile.gif" border="0">