Having that commitment in place requires MONEY, and for you to be able to have need blind admissions, you have to have funding in place to cover that for a significant portion of the student body. Again, it's not an accident that schools like Harvard, Stanford, Vanderbilt and other high endowment schools are offering this, while Miami, with a fraction of the endowment doesn't. You can't just offer it for athletes, you have to have it in place as a general student body program. Miami has around 12k undergrads, Vandy about 7,200. Think about that.
A bit of math. Let's say that Miami has 10% of the student body qualify for a theoretical Hurricane Promise program, where we cover anything not covered by financial aid if you fall below an income cutoff. Even if the typical kid ended up with a half ride after financial aid, we are looking at an overlay of around 30 million dollars per year(and i'm just including tuition cost in my calculation, not room and board). Think about that. That's 300 million per decade.