First you have to have money to invest. Then you have to have enough money to make it worth considering the transaction fees. The bottom part has debts, not spare cash for investing, so the stock market is almost completely irrelevant for them.

If you inherit $1m+, you can live off of that and not work a day in your life (or at least severely increase how much money you save) while the rest of us toil away as wage slaves for 40+ years.