I think it is about risk, not necessarily voaltility. For example, you could own a stock in a solid company or mutual fund that plods along, maybe just holding its nominal value, maybe just keeping up with the rate of inflation. Low volatility.
It’s also about magical future revenue, especially for revenue-less stocks, like a lot of biotech startups.
UST’s are considered risk-free (so far) as the US gubberment hasn’t defaulted. The PTB always keep the casino paying out. E.g., Timmay.
One year return = 24.38%
If you invested $1 million in the average S&P 500 stock index fund, you'd be smoking fat cigars and doing $243,800 worth of hookers and coke.