They're safer because the coverage team pursuers and the receiving team blockers start only 5 yards apart, so you don't get 40-yard sprints into wedges.You can either increase returns or you can reduce injuries. This rule does not do both of those things.
I may be confusing the XFL's kickoffs with the USFL's kickoffs. I went to a couple of Showboats games and was intrigued by the kickoffs. They kicked off from the 20. There was much skull cracking going on during those returns.They're safer because the coverage team pursuers and the receiving team blockers start only 5 yards apart, so you don't get 40-yard sprints into wedges.