Deepbuffet, that sounds pretty reasonable to me! Never thought about it that way before.
I'm not actually afraid of heights in the traditional sense (i.e. I will climb ladders & trees, and will enjoy the views out of tall buildings). However, if I am in a tall building with plate glass (floor-to-ceiling length) windows, I get uncomfortable if I stand too close. If I'm on the Empire State building, and looking out over the city, it's fine, but if I look straight down. . . .forget it!
It is funny how the perception is completely different in an aircraft.