From the perspective of someone who funded his SO during her writing up year (where she did hers it was expected that there would be 3 years of reserach and then up to a year of - unfunded - writing up)...
Because many people doing PhDs have spent little or no time outsisde academia, their world and attitudes to it are shaped by that. As someone with only one degree and a couple of professional post-grad quals, I find meeting up with these people refreshing. They get to travel (in 2007 Dr North went to 9 countries), and have a "young" attitude. It is not nearly as prosaic as working, where success is measured differently.
A PhD (unless you're doing exercise physiology, it would appear..! ) is hard work, and Dr North certainly put the hours in during her time, both for the research period and also in writing up. Don't assume it will be like all other taught degrees where there are answers and long holidays. This one is up to you.
As others have said, the money isn't great, but you'd be doing it in a slightly unusual area: effectively you are working in the theoretical side of counting people and studying behaviour (as I understand operaitonal research). Plenty of people with OR backgrounds become business consultants, and it is evident that it is possible to do this together with academic research. Taht's a function of your field. m
Academic life is flexible - Dr North is quite capable of dictating where and when she works, even though she is now some years out of her PhD. Mind you, she's a bit odd in that she works cross faculty and doesn't do research.
But... the egos are huge - far worse, I think, than anything I have to deal with, and I work in that most "Type A" of worlds: I'm a corporate lawyer.
There is a part of me that enjoys the cerebral side of things more than the dull, practical and repetitive world that I inhabit. SO, a PhD appeals. However, for me, it would have a significant detriment to my career and earning potential. However, it would help me escape from law hell..!
I say do it. Would be a great way not to get a hammering in the current job market, but do follow the really good advice from those above.