If this were the case, I would expect to see a great many people who have enough money already such that they don't need to work anymore doing just that.
But that seems to be quite an unusual case. Certainly nothing like 90%. What I see around me appears to contradict the hypothesis. Not just "rich" people, either. In the UK, a few hundred thousand pounds in total would (going over the last couple of decades of returns on pretty dull investments, although over just the last decade significantly less would do the job too) pay rent and bills forever if all you didn't engage in expensive hobbies, and a lot of people have that kind of wealth but are still working jobs.
But that seems to be quite an unusual case. Certainly nothing like 90%. What I see around me appears to contradict the hypothesis. Not just "rich" people, either. In the UK, a few hundred thousand pounds in total would (going over the last couple of decades of returns on pretty dull investments, although over just the last decade significantly less would do the job too) pay rent and bills forever if all you didn't engage in expensive hobbies, and a lot of people have that kind of wealth but are still working jobs.