What is it about the prisons of the empire that make them such excellent selection grounds for heroes?
I mean, the empire is generally shown as being a mostly benevolent entity in a world filled with insane demons and cultists and fucking cliffracers, so the fact that goddamn reincarnated heroes and the like are being put in them doesn't entirely speak well of their justice system.
Although, to be fair, when the guards feel quite happy about killing you for stealing an apple, I can easily see how that would be the case...
The Empire follows the Lord Vetinari principle of giving criminals a chance at public service. But they aren't Vetinari, so the heroes are just as likely to steal everything in sight, turn into a vampire, and slaughter entire villages.
The people who are clearly not members of decent society just get killed on sight. Everyone else serves a few days in jail. But if the guards see you walking around town in Daedric armor accepting quests from beleaguered widows, WA HEY, It's press-ganged into saving the world with you, you adventuring nonce, and if you give us any jib we'll cut you up a treat and ditch you in Nibenay bay for the slaughterfishes! You're the Nerevarine now! Good luck to ye, my boy!
The prisons were never anything better then a front for getting people addicted to skooma, Vivec's tyranny knows no bounds.