I believe it's more about the comfort of regular employment which is more and more cozy and attractive (including from a financial perspective). Startups are risky and intense and for a lot of people the extra stress just isn't worth it. They can be happy with a regular 9-5 job and more free time for fun and hobbies.
Culture is another thing. Society does not value success as it used to be, the self-made rich are reviled while luck, conformity and integration in society held in high regards. Unfortunately this comes exactly as future's challenges can only by solved with courage and entrepreneurship...
Then I bootstrapped my project myself and it was enough of a success to allow me to not work... It could have been a far bigger success with funding.