This dates back to at least Ancient Rome, where slaves would fight each other in the Colosseum for the amusement of spectators. Many people volunteered (actually seeking enslavement) because being a gladiator led to glory and riches.
Flamma was granted his freedom 4 times and refused it every time! He refused to quit and ended up dying in his 30s. The idea that someone would voluntarily rejoin the game show of death is very realistic.
https://en.wikipedia.org/wiki/Flamma
That being said, many gladiators didn't really have the skills to pursue a different career after retirement.