It's also a convenient way to justify not saving enough.
I've watched fairly successful business owners make this mistake many times - they were making 400K or 500K (in some cases, millions) a year off a business, but not saving anything because they still expected it to grow a lot larger. If it fails to grow, then end up either broke or in debt.
It's inherent to entrepreneurs that they believe in the big future payoff more than average, but that's also a big blind spot for financial planning.