Well, if I misinterpreted "not everyone can be a doctor or a lawyer. Some people who have no chance of getting those nice jobs[...]" then I'm sincerely sorry.
And no bootlicking, just...some people do this instead of becoming a doctor or a lawyer, and for very valid reasons (which I thank you for partially enumerating) and it irks me when people imply that academics couldn't hack it as doctors or whatever, which is where I thought you were going with that. Very sorry if I was wrong.
Insofar as it's educational to the OP, I feel it's important to note that many of the jobs which he finds so mystifying are desired for reasons entirely ancillary to either their necessity or their accessibility, (and which are hard to see from the outside, to be fair). They can be fun and engaging, too, not just dirty but necessary.