Why do people burn there lawns every spring I see smoke from people burning the grass on the lawns why do they do this?

to burn all the old dead grass clippings, so the lawn can start fresh. There is also the hope that any seeds from weeds and/or stickers might burn along with the dead grass. If the grass is thick and is never raked, a layer of dead grass builds up and air is cut off which may also result in a layer of mold and other diseases damaging the grass.