Arena Combat

Is the Fleshing pits just some sort of capital punishment for prisoners in Noxus or is it something that Noxus practices which is culturally derived like the Romans did with the Coliseum? Does Noxus capture people and put them in the arena to fight to the death or what? Or is it only for people that they deem could be worthy so they put them in there as a test? I never quite understood the cultural reasoning behind the Fleshing aside from it being just an amusement for Noxians to watch at their leisure time. Does Flesh bring economic revenue to Noxus as well?