The thing to note is that as far as traffic lights go, I already knew this. I've heard much the same thing through other sources.
And yet I still press the buttons. Even at crossings where the light never changes from "Don't Walk" to "Walk" I'll keep hitting it in blatantly false hope. (I live near one of those, by the way. Technically I can't cross the street to get home without jaywalking.) So yes, I guess you do have to grasp at straws sometimes in order not to feel helpless.
Door close buttons on elevators are a different subject. I never press those in the first place, because if the door closes on someone trying to get on I don't want to be blamed.