Let's say that you are a young distance runner with impact talent, a great student with a high GPA, and your parents make a halfway decent living - about $150K a year.
If you were shopping for a college, your local state university offers you a full ride based on your academics and athletics. This school is a lower tier D1 with a mediocre program and facilities. You might catch lightning a time or two and qualify for NCAA XC if everything aligns. Chances are that your season ends at regionals each year.
Because you are a great student with middle class parents, Stanford reaches out. Between merit aid, grants, and endowment money, your net cost to attend a storied institution adds up to only $12K a year. In addition, coach sees potential to make the varsity 7 within a year or two and offers you a preferred walk-on spot.
All things being equal and your folks willing to foot the $12K, what offer are you going to select?
How is this any different than what happens in high school? You would attend a public high school in your neighborhood. Nice enough school with the usual mix of students, semi-engaged teachers, and a running program that makes it to state every four years or so. The coach, the third in ten years, is an English teacher by trade and recently completed a 1:47 half marathon using the Galloway Method.
Just 20 minutes away is St. Jakob of The Holy Threshold, an elite Catholic school that seems to win state every year in most sports. Awesome academics, amazing facilities built by wealthy alums, and the head XC coach is nationally respected with an NXN title and St. Jakob's has made five straight appearances at the big dance. Even graduating JV guys get D1 offers on the regular. Since you are a great student and you nailed their admissions test, you qualify for the Archbishop's Scholarship which knocks the cost of attendance down to only $4000/year.
Mom and Dad can swing the $4K, where do you want to go to high school?
These are easy choices for both athletes and parents. If you can swing it without any heartburn or financial stress, it's a no brainer and the private school really doesn't have to actively recruit because the value is very apparent.