content: The extra cost for material won't be attractive as planes are already really safe, so this only is attractive for the passenger that is really freaking out and is willing to pay a lot more for their ticket. As most won't do that(see budget flights) the market is too small to efficiently earn back the investment on a plane that is being produced on a small scale. And the most dangerous parts of the flight are during take-off and landing during which the parachutes won't be able to properly deploy in time.