> if every individual investor bought the S&P with leverage
You could also go broke! (or at least significantly underperform historical averages.) Sure, you can make higher returns by taking more risk. That's not most people's tolerance in a retirement portfolio.
There are plenty of other ways to diversify besides a 60-40 portfolio that are a lot lower risk.
If you don’t want to work a job for 50 years because your portfolio got blown out, don’t buy stocks on margin. At least that’s what people who have been “educated on leverage” do.
You could also go broke! (or at least significantly underperform historical averages.) Sure, you can make higher returns by taking more risk. That's not most people's tolerance in a retirement portfolio.
There are plenty of other ways to diversify besides a 60-40 portfolio that are a lot lower risk.