If on a (very) long term, Nasdaq or S&P500 are on an uptrend (positive expected return), why are Leveraged ETF AUM (like TQQQ or UPRO) considered tiny compared to QQQ and SPY?

These are too risky and not fit for long term investments:

https://www.investopedia.com/terms/l/leveraged-...

Two reasons that jump to mind why smaller AUM for the leveraged versions compared to vanilla:

There may be a lot of folks doing leveraged buys outside (ie own broker allows margining of QQQ/SPY) and so you can't actuallly see the whole picture.

Also, levered investments isn't for everyone - it is for the more aggressive risk seeking investor, so perhaps the starting universe size is just going to be smaller.