Work from 20 to 50, save 30%, and expect to live from 50 to 90 off those savings? I can do the math on my fingers to see that's not going to work.
You can't calculate compound interest on your fingers, is the problem.
Even if someone saved 100% for 30 years, inflation will ensure they can't live off that for 40 years afterwards.
I don't think that most people save by holding onto cash, as you're suggesting.