Why Don’t People Read Signs?

I’m sitting in the airport in Toronto waiting for a plane to Dulles. Gate 97, a sense of deja vu. I was last here a year ago, coming back from a pleasure trip in Montreal (although I was heading to BWI then). This gate is the end of the line of a long walk–a good thing, actually. Going through security, I noticed a sign telling people going through security to keep their shoes and belt on, and to keep things in their pockets (there were many signs saying the same thing). Most of the people in front of me were taking their shoes and belts off. I turned to the woman behind me and said, “Doesn’t the sign say to leave your shoes on?” “They’ll make you take them off anyway,” she said, knowingly. I then looked at a woman in a security uniform on the other side of the conveyor. “Leave your shoes on?” “Yes.” Behind me, people were taking their shoes off, as they were in front of me. Why don’t people read? Here all luggage goes into a plastic bin though.