Some of these actually do have an effect, but it’s difficult to impossible for a person to know whether this particular one is a placebo button or not.

This is especially the case with elevator close door buttons. Those buttons are always hooked up, because they are needed during emergency operation with the fireman’s key. They are sometimes programmed to cycle the doors marginally faster under normal circumstances, but more often aren’t.

Also, some of the traffic crossing buttons don’t make the walk cycle come sooner, but they occasionally are needed to insert a walk cycle at all, because some intersections don’t trigger a walk cycle unless the button has been pressed.