Why do kids like Halloween treats?

kids trick or treat because they like knocking on doors and people open, when they say trick or treat. They say trick or treat because they want sweets from stranger, but you only go to houses that have lights in the room because if you knock on a door when the light is off they will not answer the door or they might be very mean to you. So never go to houses when there is no light in the house or you know what will happen...