I once made a point of reading & counting every sign around a bus door. There were 18 signs. Somehow I'm not surprised nobody reads any of them: so often irrelevant for all practical purposes, we've been trained by the signs to not read them. Ergo I won't fault anyone for following their warning-sign-induced preprogramming to give warning-like signs little more than a cursory glance, even when admonished to really pay attention this time.