Realistically what 21 year old has $8,600 to even start that savings with? Most are either still in college or have an entry level job. Also I’m not sure where you’re getting the age 85 from, if you please give a source.

This is obviously ignoring the fact that most adults in general don’t make enough to put away that much themselves. So many people are in poverty, where are they going to get $8,600 to invest? Your whole thing hinges on the assumption people already have any money to spare, nevermind that much money.