I think you're agreeing with me? Working in a lab doing research and getting a stipend while getting a Ph.D. is getting a Ph.D. - it is how you do your research.
Yep- for most people, doing the PhD IS their job.
I think you really have to question whether a program is worth it if YOU have to pay for it. (Hint, hint cousin getting the PhD in Sign Language Interpretation- 100% out of pocket for tuition, no stipend for living costs.)
In my field (Measurement, which I guess is a branch of education, so part of the exception someone posted, but we are NOT teachers, I work in a corporate environment) it is not uncommon to work a full time job while doing your PhD. In fact, I'd be stupid to give up my job to go back to school. If I was lucky, I get a $10-20k stipend in addition to tuition. But my job pays many times that, and my company will pay $25k a year towards a PhD. It will mean NO LIFE during the duration of the degree, but makes a lot more sense than leaving work for it. You don't get time off for writing, but can get flex time for classes. Of my 10 member team, 3 have done their PhDs while working, and 2 are currently doing them.