Every culture has a way to celebrate their festival. I do not see anything waste in this nor it is superstition. During marriage couples wear flower garland and throw it in the dustbin next day. When we welcome some guest we decorate and keep the house clean and tidy. It is what all the people of Kerala do. It is such a treat to watch and enjoy. You have every freedom to discount the story as superstition. I firmly believe that it is victory of lower self ( ego - which can be called Maha bali since ego is usually arrogant, forceful and poweful expression). Lord Vamana stands for higher self. The ego can never be killed but it can only be tamed. Hence Lord Vamana does not kill Mahabali.
