First off, it can become a projectile. So can a baby in someone's lap. Bags are usually secured overhead or under seats.
But if you are so busy reading or playing a game, maybe you didn't take the time to locate your nearest exit, or how to use oxygen (do you have to pull hard enough to pull a pin or not?)
And during the moments of takeoff and landing, if you are engrossed in playboy on line and don't hear: BRACE FOR IMPACT, and you get hurt, who's fault is it?
IS flying so Blaze` that a PED is more fascinating?