It could be that my estimation of other people's elbow angles are incorrect. When I place my hand above the numeric keypad, my elbow angle is about 100 degrees. When I move it about 10 inches to the right, it increases to about 120 degrees.

This might be because of my typical seated posture - I lean quite far back in my chair.

If, however, I slouch forward towards my monitor, with my shoulders off the back of the chair, the increase in elbow angle when moving my hand 10 inches to the right is much smaller.