In all seriousness, the reason you're allowed to have your bag under your legs during flight, but have to stow it overhead or put it under the seat during takeoff and landing is that all access to the emergency exits needs to be unobstructed during takeoff and landing. You cannot leave trip hazards behind for your rowmates, and you cannot obstruct aisles. This should never be allowed during take off and landing, and considering it impedes cabin service and access to the lavs, I'm surprised it would even be allowed during cruise...