i don't know how much other people have to look to keep themselves upright

Not very much; on the other hand the lack of mirrors require me to pay more attention in order to be aware of what's behind and beside me. (This is partly compensated by the fact that, not being in an enclosed space such as a car, I can hear better. But if we go down this road we encounter differences between people in how they process visual vs auditory input, the fact that Feynman counted in his mind by listening while Bethe did by reading, so that Feynman could count while reading but not while speaking and vice versa, and so on, and so forth.)