@zc17bills Well yeah if you're looking at it from 40 years time. But that's not the same as saying "you pretty much are set to get 8% returns every year" - because it's basically saying you're set to get this... unless if you don't.
But anyways...
You mention "Why doesn't everyone
annually dump their investments into the S&P"... and to be honest, I'm not sure what this means (e.g. does it mean to only stay in investments for 12 months before selling them and using the proceeds to purchase SP500 index funds)?
But isn't this already the most basic, vanilla of investments - outside of bonds and a savings account? Many retirement plans are already set out this way for people with zero interest in the mechanics of investing and just want a passive auto-pilot way to have some kind of investment pot.
But for people actively engaged in the investing space, to nevertheless still rely on a vanilla 8% return on average, to only begin to see the benefit after
40 years...
What's even the purpose here - for a fresh 18-25 year old to only focus on their old age retirement?
Considering their youth, and flexibility to take risk, isn't this incurring huge opportunity costs and wasted opportunities to elevate themselves ahead?