At ordination, why is obedience made to the bishop instead of the pope?

The ordained man understands that his obedience to the bishop is in concert with the bishop’s obedience to the Holy Father. The pope’s authority covers the whole Church, including bishops and priests. Practically speaking, though, each priest is accountable on a daily basis to his bishop (and religious superior if he belongs to a religious order). The pope cannot oversee the behavior and ministry of every priest in the Church. Each local ordinary (bishop), though accountable to the pope, has a certain freedom to minister in the way he determines is most effective given the unique needs of his diocese. His priests are expected to cooperate with him in this, so they promise to obey him.