If the market only goes up over time (or at least has over the past 100+ years), why is TQQQ considered a “short term investment”?

Like wouldn’t it make sense to buy it now (yeah yeah yeah DCA blah blah blah) and hold it for the next 30+ years? I’m only 24 so I have time to eat shit for a few years in the meantime.

It’s up 230% vs QQQ’s 109% over the past 5 years.