Jerseys are nothing but body tight tank tops these days, leaving nothing to grab. Modern helmets are so perfectly fit and comfy, they are used as weapons or encourage diving "shoulder first" at lower extremeties. It's dangerous to the ball carrier and the "tackler". Players are looking for ways to tackle guys who are bigger and faster than ever. I think tweaks to uniforms / safety gear has made the game more dangerous instead of safer. Players used to break their beaks when they led with their heads. Jerseys these days are so tight they have to make players almost like silky grease when being brought down. IMO...That leads to alternative ways. Like what the Niners are doing. It's not just the Niners. I saw a Bengal do the same thing just this past week.