A dumb sign that we actually need
Just because a sign is dumb doesn’t mean it’s not necessary. We can’t imagine what sort of disastrous event took place to force management to put this sign up. Did someone actually fall down the elevator shaft when the doors opened prematurely? If that’s the case, someone’s going to get sued.
In fact, we should all start to see whether the elevator is there before stepping in, regardless of the presence of a warning sign. Elevators are dangerous contraptions that can only support two or three Americans at most. Make sure you treat the metal deathtrap with the respect it deserves.