That's just what the numbers are, the typical 'middle class' person puts cumulatively X during their lifetime (adjusted for inflation), then after they retire before they die they get paid Y ~ 3*X.
You could be the exception of the small group that gets less than they put in, but that's not typical.
Well with the average american males lifespan being 77.4 yrs,if they retire at 65, they will never get what they paid into it unless they surpass 77.4 yrs by a large margin