It's a conceptual thing.
It doesn't require deliberate enforcers. All the enforcement is in our preconceptions and prior experiences of the words.
I'm a fan of reskinning too, but the dark side downside of stereotypes and archetypes is that they sometimes contain baggage. While the upside is that they help us picture and conceptualize things quickly due to our prior knowledge of what certain words and names indicate.
It seems like FrozenNorth's DM in that 4E game got trapped in his conception of what a Rogue is and inadvertently trampled on FN's character concept, treating the PC as a Thief when that wasn't the intended character type.