You've probably been in the following scenario before: you're sitting in the aisle seat with your tray table down, scarfing down on snacks and listening to music, when your middle seat neighbour decides it's an ideal time to tap you and mouth, "Can I get up?" You then must stow away your snacks, slam your tray table up, and brush the crumbs off yourself before unbuckling your seat belt, standing up, and having to get up yet again once they return from their bathroom break. If you're a window seat traveller, you never deal with such crumby scenarios, as you only get out of your seat when you need to.