You save for Christmas, Cars and Houses. You do that in a bank.
You invest for your future and retirement. You do that with property, bonds and equities.
And what percentage of the population lacks the knowledge, intelligence, and/or interest in developing expertise in investing and stock trading? What percentage can afford to put just a few dollars away each week, if they had compounding interest as an incentive to do so? That incentive will get a percentage of the population thinking about their budget in a better way. The rest depend on investment counselors who make their money from their clients' accounts. Or they get sold uninsured annuities that so far haven't been a problem. I wonder how many people who depended on others to manage their account were told to sell their most overpriced stocks when the market went tangential. Anyone not managing their own accounts might not have known to sell something if the money is needed in 2019.
I know you mean well. But for most people, "let them invest" sounds an awful lot like "let them eat cake".