My sister, after abandoning the Berkeley Phd astrophysics program, ended up [with no programming experience] programming those Visa mainframes that process billions of transactions a night — in assembler! I asked her once if she used any of her higher math from college, calculus and such. “No,” she said, “we pretty much just add and subtract. On rare occasions we’ll get really abstruse and multiply or divide.
Which is tangential to the topic Steve, et. al. were discussing, but keys right into something that I was thinking about. I have two degrees in Chemistry, B. S. and M.S. I worked in industry from early June of 1968 until the end of November in 2008 - a tad over 40 years. If you aggregated all the time I spent doing actual chemistry, it might total a few months; certainly it was far less than two years. If you aggregated all the time I spent doing things where my knowledge of chemistry directly informed my ability to function, it would total somewhere in the range of 15 to 20 years. Dealing with Mechanical Engineers threw this into stark relief. A typical Mechanical Engineer simply would have been incapable of doing my job. Just as I would have been incapable of doing her's - for that 30 to 50% of the time, unless I received some amount of specific training.* Also, I'll posit that specific engineering knowledge was a relevant enabler to the M.E. no more than 50% of the time.
Here is a related anecdote. Some of my musician friends are employed as computer programmers. Their education is in music. Their employer specifically seeks musicians because training them is especially easy. There is some sort of fit between the musician's mind and the tasks to be performed.
My point is that doing something other than what you were educated to do is not a misuse of talent, except in the most egregious examples - frex PhD' physicists driving cabs, Engineers delivering pizzas, Accountants digging ditches, Economists doing economics. (Sorry, couldn't resist the dig.)
Realistically, your education does not prepare you for the world of work, and most specifically, the chance of it preparing you for the job you actually get is almost vanishingly small.
* Some of this is skill and training related, and some has to do with individual brain idiosyncrasies, interest level and willingness to learn. I'll bet I could learn the M.E.'s job with very little additional training. Engineering is applied math, and I'm reasonably good at that. Not so the other way around. At the briefest mention of anything remotely chemical, the M.E.'s eyes glaze over. Persist, and they will run, screaming, from the room.