I have been taught to do a great many things; drive a car, ride a motorcycle, fly a plane, martial arts, boxing, close combat shooting, and several other fairly dangerous things. The thought never crossed my mind that I should start training to be an instructor of ANY of those things when I was just learning myself. I didn't even want to look past rescue as a diver for some time and many dives. This mindset of rapid advancement to be able to teach others to do the same is just scary.
Psst: The difference is that dive certification agencies make it EASY for pretty much ANYONE to become an instructor or at least a DM. (I didn't say "good" instructor.) It isn't really necessary for one to gain years of experience to become an instructor. In contrast, some of the activities you mention require years of study and practice to become good enough to instruct other people.
I think that some people see becoming certified as an instructor or DM as a way to feel good about themselves--becoming certified at SOMETHING. It's a trophy credential, and it's a much easier and faster credential to earn than, say, a "flight instructor" credential, and "divemaster"/"scuba instructor" sounds more prestigious than "driving instructor." People are attracted to doing easy things that make them feel good about themselves. Not everyone can be a rocket scientist, but pretty much anyone can be a DM or instructor. I think there are people who earn the credential first and THEN think about whether it's the career they really want.