General license HAM operator here. The good thing is that HAM licenses are trivially auditable as the FCC provides a direct lookup on anyone licensed so anyone at all can verify their status. HAM bands are typically enforced by fellow operators who will work to triangulate and locate people who shouldn't be on it. There are even organized competitions where they practice locating devices.
I think the habit arises from people assuming ham was also short for something like AM and FM is, or in computers, since PC was an initialism, Mac should get the same treatment too.
