Because let me paint this picture, and you're right in away. But me calling it out might be what saves me.
But when D1 ended I figured one of the two strongest players would die.. by strongest I don't mean this exact game, I just meant mafia. That's Chris or Jeff. So I asked myself which was the most likely. So I picked Chris, and me having the doctor role means either 1. I made the right choice, and protected Chris, or 2. They didn't try killing anyone in the middle of the night.
But me being town, and being doctor who protects a player, then there has to be ways for scum to kill during the night. Now where it puts my life at risk, they know now I can protect a player at night, they might take me out tonight to stop it.