C'mon people; understand what NIL deals are, which are private business transactions. Players get paid by a company to endorse product so they can sell more. It's not dependent upon or limited to college play unless the deal is structured that way. In fact, being endorsed by a player who just went pro is probably much more lucrative, so why would the business limit themselves as you suggest? It's also illegal in some states. You want them locked in, petition the school to structure scholarships that way and good luck with that recruiting strategy.
You would think their time at UT making millions for the school, putting the team back on the map, living & breathing football for three years would matter to thankless fans.
Their "time at UT, perks, free room, board, and education" wasn't "free" - FFS - it too was a business deal and the school got a steal of a deal. Opt-outs are opting for a better opportunity, just like coaches, administrators, and everyone else in society.