I think they don't want to engage in NIL, because they know that it's not a way to get a competitive advantage.
Prior to NIL, recruiting was heavily tilted towards blue-bloods. If aggy wanted to gain an advantage, breaking the rules by paying players gave them a leg up on a large percentage of their competition. Even more so by breaking the code and spending way more than anybody else.
Now, if they switched to NIL instead of bags, they'd hypothetically be on a level playing field monetarily with the competition, but at a disadvantage in all the other areas where aggy is deficient (location, culture, historical significance, etc.). So there's nothing there to give them an advantage. They're hoping that the bag game will give them a competitive advantage - especially against all the schools that have moved from bags to NIL . They will try to sell players on smaller bags now being better than big NIL payments later, and then hoping that payments to the handlers/uncles/trainers will help direct the players to aggy.
What's amazing is that they got Hicks and Hill to sign, so they'll think that their plan is working. It's just bad luck from a season gone sour that is causing recruits to jump ship, and they'll probably try clinging to the bag game for an extra cycle or two.