This situation was caused by intricately intertwined reasons, i.e., the fact that shinabe, which was the remnant of the bemin system, itself was incompatible with the ritsuryo system, that it became difficult to preserve shinabe as the ritsuryo system was weakened, and that improved social economy standard enabled procurement from and koeki (forced labor under the ritsuryo system) by ordinary citizens (procurement from ordinary citizens here includes procurement from commercial and industrial men in former shinabe).
これは古い部民制の残滓である品部そのものが律令制と相容れなかったこと、律令制の衰退によって品部の維持が困難になってきたこと、社会経済水準の向上によって民間からの調達・雇役が可能になったこと（この場合の民間には旧品部の商工業者からの調達を含む）が複雑に絡み合っていたと考えられている。