There have been lots of expensive changes made to automobiles for safety purposes, most of which increase the cost of the vehicle. Examples include seat belts, bumpers, front & rear crumple zones, air bags, side-impact beams, collapsable steering column, steel chassis, antilock brakes, winter tires, wiper fluid with antifreeze, positraction, 4-wheel drive, roll-bars. Cars that burn methanol even mix in 15% gasoline so that if there is a fire, the flame will be visible!

All that for safety. Pretty expensive. Think how much we could strip down a car (or an airplane) and still make it go. Cheap, but dangerous.

Aircraft that burn liquid sodium borohydride as fuel would be one more upgrade. One day people will see that it makes sense.