I have a PhD, because at the time I wanted a career in academia, and I enjoyed research. I did a short post-doc, because I still wanted a career in academia, and enjoyed research. I quit academia because I no longer wanted a career in academia, and I didn't enjoy the research (or my boss).

I don't regret my wasted years. Sure, I would have likely earned more money, but it was fun, and made me who I am.

I do find it a bit of a shame that my current and previous employers couldn't give two hoots that I have a PhD etc, but oh well.

EDIT: I have a PhD and post-doc experience in Cell Biology, and now work as a software engineer at a fairly large hardware company.

I trained and qualified as an Industrial Electrician (not on the same scale as a PhD academically but not a trivial amount of work to do either) and decided I loved the theory and hated the practical.

I'm a software engineer and none of that training has ever been directly applicable (though some of the engineering and planning aspects generalised have).

I have found it a bit frustrating that I am more junior on the company scale than most people my age. In some respects, I have lots more experience with people my pay grade, but in others, not so much.