It does seems strange. Our culture of autonomous freedom makes it stranger still. So then, why?
It goes way, way back. To the concept of disciple. To the understanding of a man or woman coming to a holy teacher and saying "Teach me the way to God." The idea being that this person had found the way to holiness, to righteousness, to union with God. If he (or she) tells me what to do, and I do it, I also will come to God. It is the ancient human awareness of the need of a mentor, a teacher.
And so, throughout history, and also in the early Church, people would seek out holy ones to learn to live radically for God. In the Church, we see this in those who went out into the desert, seeking to live the way of St. Anthony of Egypt, of St. Pachomius, of St. Arsenius and of St. Moses, among others. They would live near a holy one, learning the way of God.
But it foundered once the holy one died. The teacher was gone. Sometimes another teacher would come, but sometimes too, the community would disperse. So then you have the fathers creating a Rule.
St. Benedict's Rule was the most influencial in the western Church. In the development of a Rule, the person now had something that outlasted one human life. It was a clear statement of life - "if you follow this way, you will become a saint." It provided stability and a certain objectivity. No more the way of one human person, which inevitably included also foibles and failures. Now it was a permanent, stable, clear way to follow.
Of course, once you have something written, with a group trying to follow, you have to have an interpreter, a guide, to teach the way, to explain, to clarify and to guide - hence the election of superiors. These men and women now move from being the teacher and exemplar in the sense of the "master" of the past to being the interpreter, the safeguard, the guide of the Rule. Hence, any superior on installation in office is told that his or her "job" is to guide the community according to the Rule.
And every vow of obedience is made "accroding to the Rule."
"I want to be holy. I vow and promise to obey this rule, which is the way of holiness. I vow and promise to obey the superior as she commands according to the rule." If you ever have the opportunity to witness the vow ceremony of a religious community, listen to the words of the vow. You will hear these words (In appropriately modified form.)
Why would you vow to obey? Only to become a saint.