The origin of the superstition is believed to have come from the facts: unless putting them away soon, dolls and silk handicrafts were eaten by bugs or damaged by mold, for Hina-matsuri was held right before the spring rainy season according to the old calendar.
旧暦の場合、梅雨が間近であるため、早く片付けないと人形や絹製の細工物に虫喰いやカビが生えるから、というのが理由だとされる。