Why don't they?
WHY DON'T THEY PUT EMERGENCY BRAKING PARACHUTES IN THE TAIL OF AIRLINERS?
Silly?
Not so silly as arriving at the golfcourse in a 747. I can immediately think of two airlines that would have been very grateful for an emergency braking parachute in recent times. I'm sure there are many more.
Sure, I know, if you get it right EVERY TIME you should not need one. But how many lives and dollars have been lost already when aircraft overrun the runway?
Humans sometimes malfunction. And so does machinery.