...because it's Treason, the one crime that every nation in the history of the world has said is punishable by death? (okay, I don't have any research on that)
Stabbing a ruler is also treason, got a Auto Ban for that? And no treason was not always punished with death, depending on the standing of the noble and their power, life in prison was also an option, and in some cases they were even pardoned.
