A lot of people make bad decisions with money: over spend with credit cards, live beyond their means, have more kids that they can comfortably support, etc.
I am single and not a high-maintenance person even though I could probably have almost anything I wanted. A life of frugal living has enabled me to save a hefty nest egg. On top of that, I get a good pension and SSI and pretty good interest on my investment in tax-free municipal securities. My car is a 15-year-old Honda, my clothes are horribly dated in regard to fashion (but who cares? I'm not going to be in any beauty pageants for sure) and I live in a house I inherited. All I have to do is buy food (which in my case had averaged about $2600 a year recently), pay for car insurance, maintenance and gas. Home utilities (electric, cable which includes phone and TV, heating oil), garbage removal, property taxes and homeowner's insurance, pay for any OOP medical expenses and take my cat to the vet once a year.
I don't have a credit card. When I open my wallet and see it's getting close to the end of the month, I know to stop spending.