Tetsunojo has attributed the reason for this structure to the fact that Sarugaku (literally "monkey music," a form of Japanese theatre performing art resembling a circus, that was popular in Japan during the 11th to 14th centuries) was compiled by Kan-ami, Zeami, Zenchiku KOMPARU, et al during the Muromachi period, a chaotic war period during which death was extremely close by.
これについて銕之丞は、観阿弥・世阿弥・金春禅竹らによって猿楽が集大成された室町期は戦乱の時代であり、死が人々にとって極めて身近なものであったことを、こうした構造の理由に挙げている。