Honestly, the fact that opening an account is easy and that there are now nice, slick, easy-to-use trading platforms has done as much as the lower fees. When I

Honestly, the fact that opening an account is easy and that there are now nice, slick, easy-to-use trading platforms has done as much as the lower fees. When I opened my first online brokerage account back in the ancient times (2005), the brokerage websites were scary, and lots of stuff still required printing out paper and sending it in. Even then, trades were still cheap (I was paying $7/trade) -- but the whole process made it feel daunting, and made clicking the 'buy' button feel scary. Nowadays, buying shares is almost as easy and fun as buying shit on amazon -- and when you couple that with the fact that "everybody knows" that the reason that rich people are rich is because stocks -- it shouldn't be too surprising that everybody is racing to get in to the game. On top of everything else, we are currently in the longest and best bull market in the history of the public stock market -- which means that we have a big crop of folks that have no personal memory of stocks losing money. I frequently talk to folks that think that 2015-2016 is what a "scary market" looks like, and also frequently talk to people that remember with fear the "2011 crash". If that's what you think a bad market is like, you're going to be ready to put your last penny in.