Byproduct of the rule change:
Kick returners just got less valuable, as fewer kicks will be returned.
Good kickers becmoe less valuable, as most NFL kickers can kick the ball 70 yards (now 5 yards deep), while a lot fewer can consistently kick it 75 (what it used to take to be 5 yards deep).
Less valuable to a team means less salary.
Call me a conspirortist, but is this all about the money?
You want to cut down the speed of the kickoff team and reduce injuries? Just like a scrimmage play, no one can be moving toward the free kick line until the ball is kicked. Starting from a standing start as compared to a running start will slow them WAY down.