As a coach in little league football and with two sons who played in middle school, I will say the biggest problem that I have seen is bad tackling technique from coaches.
I used to stress constantly about the need to "see your target" when you tackle and always keep your head up, but many coaches, most who played high school ball "back in the day" just wanted the kids to put their heads down and tackle. Big hits were celebrated much more than just solid tackles with your pads, wrapping up well.
It was a constant battle.