That's what people who stay wealthy do.
Regardless of Phil's cash flow, he probably is stressed out about money because he's likely living well above his means. And by this point, he's used to the 'finer' things in life and has no plans on humbling himself into an affordable state. But living like that is how you wind up being a sixty year old walmart greeter, living in a shitty apartment and eating dogfood. Wealthy people tend to live in affordable houses and have frugal budgets. Then they spend their twilight years on cruises where they get treated like royalty.
There's different tiers of "wealthy" of course, and yeah some of them have million dollar houses and a retirement plan. But an elderly couple living in a tiny cheap place doesn't necessarily mean they're broke.
*edit*
The tragedy here is that if Phil's parents are well off, they're not going to get to relax. They're going to end up bailing out their selfish dipshit of a son and taking care of his ass until they die.