Someone considering to live a life in ordination and to request the vows of a nun or monk does it with the intention to give up worldly life with all its distraction and to create the space to practice spirituality.
The many monastic vows serve as protection, forming a fence, hence procuring us with all the freedom to live up to our strive. We may be astonished to hear that a multitude of rules are supposed to grant us freedom because actually we only know of restrictions as hindrances. But look at sports people who spend uncountable hours a day to come up to their profession or manager who spend their lives more in their jobs as with their fellow men. Both adhere to a particular system, reglementing their doing in order for their focusing to become even more effective.
It is somewhat similar for ordained ones. We want to optimize that which is the most precious to our lives by all means and optimize our strive. Only the promise not to take any intoxicants any more gives us so increcibly much space - mentally because we do not have to think about if, how, with whom and where we want to get intoxicated as much as practically: the time we would use for the contrive of possible strategies, means, etc is now being used to tame our minds and to practice spirituality.
The first step into ordained life is the strong decision to give up the life of someone bound to a household and instead live a life of absolute simplicity. If we only have some kind of affinity for the outer appearance of a renunciate or dwell in romantic ideas of monastic life we will certainly shipwreck soon and endamage the esteem of the community.
Ordination as a getsul/ma comprises the first monastic vows of a noviciate. It can be upgraded with the gelong/ma ordination making the nun and the monk a full member of the sangha, the monastic community.