i think they were simply remarking that someone had an advanced degree and it wasn't being put to use.
this point is really about the system/world/situation and not so much about individuals.
> there's nothing inherently wrong with a job that requires you to drive around all day
seems like a red herring.
Restated: If you spend 8+ years and tens to hundreds of thousands of dollars to learn something, not putting it to use is a colossal waste of resources for everyone involved. It's not just you. It's the seat you took from another student who would have appreciated it more.
Knowledge itself doesn't contain any inherent value, it's free if you want to learn it all yourself without depriving anyone else of it. What you're paying for is the academic environment, resources and tutoring of a person. That's a business exchange like any other and everyone is free to spend their money on that, whether they do anything with the results or not.
I am not against the viewpoint you present for anything other than what I see as pragmatic reasons. If we lived in a post-scarcity economy, I would agree with you.
But we don't, and we aren't going to be there anytime soon, either. The system we have now loads crippling debt on to students, and one of the reasons it can do so is because of the constraints of supply and demand. Thus, in my opinion, to not do anything with an advanced degree is deeply selfish.
Either way there's nothing inherently wrong with a job that requires you to drive around all day. Work is work regardless of if you look down your nose at it as "menial".