Earlier quoted context omitted.
I notice this pretty consistently with elevators: If you press the button for a short amount of time, it visibly lights up while pressed but doesn't actually register the button-press.
I have long presumed that sort of thing to be deliberate, avoiding activation on accidental bump.
But wait, there's more: when the elevator arrives until it leaves, the button should flash or change to a more prominent color. Why? Because imagine someone presses up and someone else presses down, and the elevator arrives going up. If the up button switches off at this point, now only the down button is lit which clearly signals the elevator is going down, which is wrong.