Because there isn't much difference in the force between a 1m and a 8000m drop due to the above. So it really comes down to case, angle, and material onto which it was dropped with corners being more vulnerable.
There is. Dropping your phone follows a curve, it falling from 16,000ft it does not. There are more forces at play when you fumble your phone. They aren't necessarily stronger forces though...just more of them. Trajectory and spinning add different forces on top of gravity. There is also the catch attempt that invariably forces the phone down harder and changes the trajectory.
