Well, my personal reasons for going into a phd were because there was no upward mobility in my "field" of back breaking physical labor. I made a marginal 15-20k which multiplied out for 6 years is 90-120k. I was already a manager where I worked. There wasn't a lateral jump I could have made because after working 70 hour weeks I didn't have the time and energy to apply for "better" jobs. I was too busy living hand to mouth. The phd programs I have gotten into come out to about the same amount of money, 120k-130k of guaranteed funding, but this doesn't include the health insurance that I did not have and desperately needed or supplemental funding for summers and so forth. Nor does it factor in the actual work for wages or physical toil that jobs like working at Wendy's or other fast food/retail work necessitates.
I think that the problem with adjuncting and stale PhDs are real, but I don't think that the "risk" of getting a phd is as dire as suggested in this forum. If you're leaving a 100k year a job then yeah, maybe you should really think about it, but for most people who face persistent poverty I don't think the phd is going to reduce their income over time if it's a funded program.