I'm pretty sure "most of the population" has at least seen advertisements for ETrade. Probably too complicated for them though. That's why they'll be working until 85 or eating cat food in retirement...
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.