I understand that, and getting a Phd isn't about money, for me it is about the desire to do something challenging and interesting for your the rest of my life . But you still have to plan for the future and ask whether this is a viable decision for life outside of academics (i.e. my family, my loans etc). I love math but I also love computer science and choosing where I want to invest the next 5 years of my life does involve weighing the outcomes of these two paths. I do get your point though, people who simply think it would be "cool" to have a Doctorate or who's only motivation is money will have an incredibly hard time persevering though the gauntlet of getting a Phd.