I wonder how much usability engineering went into them. In theory, it's only two straps, two clips, three steps. But maneuvering to don it under stress in an economy seat, especially if the aircraft is pitching or rolling as you are spiralling into the ocean.... Then you need to remember to pull only one of the tabs-- pull both and you'll be to big to fit easily through that window exit, dooming those behind you, with nary a sharp object to puncture it to be found....