I think including boarding passes is a bit much. I always put mine there since it is easy to show it if an issue with seating assignments develops.
One thing that annoys me when I fly first or business class is they automatically put a blanket and pillow on the seat along with a bottle of water. I don't need any of it, yet now I have the hassle of either storing it or getting the FA's attention during boarding. So again, it often gets stuffed in the seatback.
I can see the safety side of it though.