"Why (does) the Boeing flight computer needs pitot tube input at all ?" If there is a strong tailwind, the plane needs a much higher ground speed to avoid stalls.

If these accidents prove anything, it's that we need a computer that takes many different inputs (GPS from the tail and the nose, pitot, barometer, AoA indicator, input from the pilot, engine RPM, etc) and put them into a mathematical model of the airplane before overriding the pilot.