Why do people let lanterns?

Lanterns, lights, and jack-o'-lanterns are a big Halloween tradition. They came from the legends and stories of floating lights and other stories for lighting the way. Another reason was to let children know it was okay to come to their door for trick-or-treating. If the lantern was lit then it was okay but if there was no lantern then the house was either out of candy or not participating. These days people signal this with porch lights and lanterns are mere decorations.