I am disgusted by your presumed superiority and know-it-all air. You think you are so much more holy and useful than a lifelong cloistered nun who has spent her life in prayer and devotion to God?
Who are you, so great and holy and wise, to judge what she has done with her life?
I’m not convinced it’s a choice once they are fully indoctrinated. Hard thing for an individual to go against the Priests and the wishes of Rome when taught this is an acceptable lifestyle, and to leave would be to fail what they perceive to be a calling. Many stay because of fear of the fallout for leaving.