It's a tradition since it has been that way in one form or another in almost every single game so far. And while he's head of Bethesda, it's his right if he wants to continue the tradition. Plenty of people recognise it, and Oblivion was certainly NOT the first game with it, or else how would it be recognised by the people here as a tradition before it was announced (it was, by many)?
Todd's Tradition=Prisoner for some petty crime
Oblivion=Prisoner for some petty crime
Morrowind=Prisoner due to possibly fulfilling the Nereverine prophecy
Daggerfall=Sent on a diplomatic mission by Uriel and trapped in a cave after your ship crashed
Arena=Imprisoned by a traitor to the empire
I'm not seeing the tradition Todd is suggesting