The rule hasn't changed - it's just not enforced. Officials don't want to get scratched by a coach for making their stud player go out to fix his pants (or put kneepads in, even), and officials shouldn't be the uniform police anyways - coaches sign a card that their players are properly equipped, it's their responsibility to ensure that is so. So unless he's wearing hot pants with his cheeks hanging out, most officials just let it go. It doesn't help that at state championship games every year, even games with TASO board members as officials, nothing gets addressed - so if TASO, UIL, and the coaches don't care, why should officials? It's not like it gives an advantage to the player.
The reality is, kneepads offer little protection to the wearer. They were more necessary back with older equipment, specifically helmets, that were much harder and less forgiving- kneepads were originally to help protect the tackler from getting a head injury, in a time where helmets offered relatively little protection to the wearer.
The NCAA, and UIL, are never going to move backwards in perception around player safety, and even though they don't really do anything, they will not remove them from the required uniform.
