[Aurornis]

The ejection force is to ensure the pilot clears the airplane as they enter the airstream. Think about how much force you feel when you hold your hand out a car window at 60MPH, then remember that wind resistance increases with the square of speed. You have to be launched hard to get away from the tail.

Also the last thing you want in the critical emergency safety gear is more levels of complexity and additional things for the pilot to consider.

[HPsquared]

That airspeed is highly variable though, the plane can go supersonic or at approach/landing speed with flaps extended. Probably 10x+ less aerodynamic force going at low (indicated) airspeed.