Placebo buttons

The "close-door" button in the elevator, the crosswalk button at the intersection, even the thermostat in your office — there's a good chance that they're all placebos. Over the last 20 years or so, many (though, weirdly, not all) of these buttons have become technically useless, but are left in place both because it's expensive to replace existing equipment and because, psychologically, they still serve a purpose.