Apparel companies and schools have to prove they're not profiting off the likeness of an amateur player otherwise they could be subject to lawsuits similar to the O'Bannon one.
I know. Someone earlier stated that it was an NCAA policy. It's not. Although most teams have adopted a similar policy to what Miami started back in 2015.
That's not an NCAA rule. Miami decided to make that decision on their own back in 2015. The only jersey numbers available for purchase are #1 and whatever year it is. So #18 this year and #19 next year and so on.