Because there are still parents whose moral compass is so skewed by snobbery, status anxiety and greed that they make a conscious choice that the risk of sexual harm is outweighed by the cachet garnered by attending the most prestigious Catholic school in the country?
I agree wholeheartedly with @AllyKaneT about boarding schools generally (and I did go to one). My experience is that it is not just the students who are actually unhappy, bullied or would say they felt abandoned who suffer lifelong damage. Those students are in some ways better off, because they are more likely to face up to the damage and seek support to overcome it.
The ones to worry about are the ones who "loved it", dismiss homesickness as a normal developmental stage, are evangelical about it teaching them self-reliance and independence etc. Those who would agree with their parents that it was the making of them. It was. That's not a good thing. Later in life, perhaps after having achieved the kind of material success their parents had in mind when they sent them away, these people often have devastating impairments in their ability to form, navigate and maintain healthy relationships. They often suffer from alexythymia as a result of learning to suppress and swallow unwanted feelings. They often lack empathy, or the ability to express it appropriately. They are frequently blind-sided by mental health problems, depression and grief in middle age, often when their own children reach the ages at which they were sent away.
Boarding school DOES work in the way that parents hope it will - but often at a terrible price. The healthiest choice for any child is to live full-time with adults who LOVE them unconditionally and have their interests at heart. No boarding school can offer that.