A TIME editorial writer didn't know, but I can suggest a few reasons.
I found myself reading from the online version of TIME magazine an essay about why nuns are an “endangered species.” Allow me to paraphrase the essay ruthlessly, so as to spare you the distress and aggravation I myself suffered when I read the whole piece. In brief, the article says that:
1) No one is becoming a nun anymore .
2) No one is becoming a nun anymore because the Vatican is mean to nuns.
3) The proof that the Vatican is mean to nuns is that the Vatican won’t let nuns become priests.
4) No one is becoming a nun anymore because all the cool reasons for which young women used to become nuns can now be realized by young women without suffering the indignity of enduring the Vatican’s lack of appreciation.
Point 4 is worth considering in some detail. The author wrote:
Get it? Young women used to become nuns so as to live as upper-middle class First World professionals, but now they can do all that while working for an NGO or the federal government, so why put up with all that Vatican hassle?
Notice what the author did not mention. She did not mention women entering religious life because the vows of poverty, chastity and obedience are a path to holiness.
She did not mention women entering religious life because they wanted to live as a consecrated bride of Christ.
She did not mention women entering religious life to find the consolation of communal life.
She did not mention women entering religious life to live the charism of their order’s founder (e.g., loving God in simplicity in the manner of Saint Francis, loving God in truth in the manner of Saint Dominic, etc.). One has to wonder—why not?
With that question, I turned to Saint Paul. He writes:
The author of the TIME magazine article did not mention the properly spiritual motivations for women entering religious life because she either could not see them, or she saw them but could not see them as valuable.
Happily, many young women today, with the aid of the Spirit of God, do see and value those motivations and do join religious communities. Go to the website of the Council of Major Superiors of Women Religious to see many shining examples of such Spirit-motivated young women.