Not sure when it happened, but the form tackle changed at sometime in the last 3-4 decades and this caused the problem.
I played a lot of ball when I was younger, and I remember being taught to break down, square up, and put your shoulder right on the guys belly button, wrap up and drive to the ground. The key to this is you have the eyes up and your helmet doesn't initiate the contact....the shoulder does. My right shoulder is noticeably lower than my left to this day...a different problem.
I remember some years back seeing a clinic about proper technique, and they were teaching them to put their helmet into the sternum. Obviously this is an evolution of vicious hitting and it's aimed at hurting more. This also puts the tackler at increased risk IMO.
If this rule takes some time but ends up with a return to the older way, I'm all for it.