Actually, you might be surprised at the absolute faith mason groups have demonstrated for each other at times. In the Mad Muad game you modded, Fox and Ravens outright lied about his roleclaim, and neither of his Lightside mason buddies turned him in.

Actually, seems pretty standard to me. While players like you and I may be more tempting, we are also more likely to be protected by the same reasoning. Furthermore, if you see all the veteran players except one or two die, then you should be extremely suspicious of those remaining. Lesser known players have as good odds of being an important role as anybody else, and they're unlikely to be protected (unless bulletproof or self-doccing) so why not kill them on night 1? And it leaves little trail that can be drawn back to the mafia.