HFT isn't a casino. It's rent extraction. Still not great, but it doesn't affect people investing for value.
Day trading is closer treating the markets as a casino. That's always been allowed. It just wasn't accessible to most "gamblers" until relatively recently. It's not "high frequency trading" in the way practiced by huge banks, but it's not a good idea.
Real casino action is playing options, using margins, and executing shorts, which use leverage to turn small gains into big ones and big losses into enormous ones. Those, too, were out of reach for most people... and really should be. That's not just giving them a footgun, but installing auto-aim. That's not high-speed trading, but it's a way to go broke real fast.
