Every 1-2 years (or after a major air crash) someone, somewhere suggests this idea. Which amounts to:
1. Aircraft to become more complex (e.g. heavy, expensive, failure-prone, carrying less passengers per unit of fuel)
2. The idea works only when aircraft is at high enough altitude for the 'chutes to work reasonably. So no profit in takeoff and landing (when most of crashes happen)
3. The idea works only when aircraft is slow enough for the "bus" and it's precious contents to survive aerodynamic hit and turbulence without having shape and controls of an airplane, rocket or something similar. So no profit at marching speed, either.
And yes, 2 and 3 pretty much cover the whole flight.
4. Bombs inside and missiles outside still invariably fatal.
Sorry. Back to fighting terrorism, training pilots and engineering better avionics.