Uh, you ever hear of taxable investment accounts? Online brokerages, mutual funds, etc?
The fact is that it has never been easier or cheaper for individuals to invest in a reasonably diverse portfolio and grow their wealth. The problem is that the average American has no wealth to grow:
https://www.cnbc.com/2017/08/24/most-americans-live-paycheck...
I am fairly convinced, based on the spending attitudes of many people I know, that even if they had extra money, they still would not invest. They would just spend it on a new 4K TV, new car, or a bigger house that they don't need. Most people seek immediate gratification.