This is explained by the theory that the values given by connoisseurs may have shifted from 'nasu' (eggplant) style tea caddies, which were considered suitable to Shoin (reception room) rooms, to 'katatsuki' style tea caddies, which were suited to small tearooms.
その原因は書院向きとされていた「茄子」から小間向きの「肩衝」へと、数寄者の評価が移っていったからではないかと説明される。