It is also the case that professional traders make a lot of money out of retail investors. The percentage of retail investors that actually make money are, iirc, quite small. It doesn't make sense to do something when you don't have the time to get good at it, and being bad at it means you're going to lose money.
Sometimes you're forced to (when an investment is tied into a basic necessity, like a house), but you're always going to be at a disadvantage.