thanks
that's what i talking about
OK. Good. I thought that you may have believed that to be the Catholic church's teaching on it from your response.
Regarding your original question, I do not know the official reason or where it may have come from, so I won't address that part of your question, but I can mention what I remember and it may shed some light on the issue for you. I grew up in a Catholic family, but please keep in mind that I am not really up to date on current Catholic teachings/practises.
The nuns are considered "married" to Christ, in the sense of total and complete devotion of their lives (not sex.) In order for a nun to completely dedicate her life to serving God, it is part of the practise that she will take a vow of chasity and poverty and redirect the energy might otherwise go toward "wordly" pursuits and apply that energy spiritually, as well as all her time, to God's service and prayer.
There are/were many Orders of nuns -- groups that have specific jobs. I do not know them all, but they include orders that focus on teaching, some on helping in the community (like operating orphanages), some devoted to almost constant prayer, etc. It is considered necessary that a nun be completely mobile to be available to go where the Church needs her to go (similar to a priest,) and with no other personal commitment than serving God in the capacity of the type of vow that she took.
I do not think that the Catholic church has the position that being a nun is an "ideal" role for women. The church has a focus upon vocation, meaning a "calling" or a way in which a particular person could best serve God -- by answering God's calling. So, for example -- being a nun is thought to b good, but not
better than being a wife/mother. There are other recognized vocations. It was not considered that a woman has to be one or the other, but that may have been typical in the past.
As I understand it, what is considered most important is that a person follow a path they believe is part of
their life's purpose. There is a lengthy process for becoming a nun. Often women begin the process of becoming a nun but do not complete it -- because either that person, or the church, comes to the conclusion that being a nun is not the right vocation for that person.
Does that answer your questions?