I think we are just exaggerating this thing with finished fighters.

Back in the days the 30's 40's and 50's A fighter would do normaly about 130 fights and those fights was mutch harder and with harder gloves and still thay managed to fight through many ko losses and still did good for many years.

Today as fast as a fighter get a big beating in a fight and even if he's young everyone starts "ooo he's finished he took to much beating"
I am not taliking about fighters like evander! Evander is done. But many aother are not.