During our Wild Damn Texan heyday drax0r and I were returning to the office from a rare offsite break where we entered our two-story office building's elevator. Just before the door closed, the only other person we'd ever seen in the building entered the car. drax0r pushed the button to the second floor.
The stranger commented that the presence of more than a single button was excessive, as a single button would suffice no matter which floor you were on, or which floor you were attempting to gain access to. drax0r agreed, adding that if you didn't know (for whatever reason) on which floor you started, a second button further complicated the process of getting to where you needed to go.
By virtue of being in the elevator of a two-story building they agreed that a single-button user interface was not only more effective, but also more efficient.
I was reminded of the time I set my answering machine to emit a single beep rather than a message telling the caller what do after said beep - we all know what to do after the beep. Unless there is no self-fulfilling message prior as it turns out, as 100% of my callers did not leave messages. When I confronted them as to why, they all explained they were waiting for the beep after the message rather than the beep itself. In my mind someone - anyone - would enter that single-button elevator and be dumbstruck as to how proceed based on a shift from the standard paradigm.
That aside, any system which is highly configurable is by that very nature also enormously complex. Self-aware artificial intelligence systems even moreso. But a single-button user interface has a power so great as to outlast and outsmart highly configurable enormously complex AIs: universal understanding. [The elevator scenario notwithstanding] any person from any age group from any culture any where would no doubt be compelled to press the only button in sight.
Its power is in its simplicity.