Monasticism started as a way of living the Gospel life more fully. The Rule of St. Benedict is very Christocentric, Christ-centered; to seek Christ in the superior, in the sick, in the guest, in the poor is not always easy. The situation may not be pleasant and/or I may not desire at time to seek Christ in the other. Yet, it is in those times that Christ is most likely calling me to go deeper, to surrender my will to His will, that is, to say with Him in the garden, "Thy will, not my will, be done." This is the very reason why the first ascetics went out into the dessert -- to renounce self and follow the will of God more definitively. It is also the very essence of a monastic vocation: to seek God, not self.
How is this lived out? It is lived out through the practice of the vow of obedience. The vow made at monastic profession did not say that I will discern with the superior for what is best for me; the vow made was obedience. It does not mean that we necessarily agree with everything the superior thinks best. It also does not mean that I am not called upon to make decisions. It means that I believe in faith that the superior hold the place of Christ and as such I hear His voice through my superior.