Usable = Usual

Did you know one theory regarding the "QWERTY" layout of the keys on our computer keyboards is because it causes us to actually type slower? The idea was that slower typing would minmize key jams on early typewriters. This doesn't make much sense in the modern era but, because it's what we're used to, most people still find QWERTY preferable over a "more usable" keyboard layout.

What if a car manufacturer decided it would be more usable to put the brake on the right and the gas on the left? What if you stepped into an elevator and there weren't any buttons? What if your dictionary was not in alphabetical order?

Sometimes good usability is as much about our customs, habits and expectations as it is about design choices.