I agree with Buddy Lee.
Some of these hits aren't the result of players trying to injure or hit someone in the head. When you're coming in at high speed and trying to hit a moving target, you can't control the small moves that target makes. If it shifts a tiny bit this way or that way, or moves its head down a little, you make contact in a way you weren't intending. That's not necessarily the defenders fault, it's also on the offensive player - they're trying to play the game and evade defenders themselves.
As it is, everything favors the offense. It has gotten ridiculous with the defense not being able to try to stop the offense. You pretty much have to start pulling up if you get close to the quarterback, just in case they throw the ball before you make contact or decide to do that BS slide thing which, for whatever reason, briefly transports them from the football field to a ballerina stage in so far as the rules go. When a runner is heading for the sidelines - same thing, the defender pretty much has to pull up and risk them making a move to gain extra yardage, or else risk a penalty for having touched a target moving 20 mph a half second after its feet happened to touch white paint (never mind the fact the defender needs to be watching the torso of that target, not their feet).
Defenders need to be allowed to try to make plays and not be hesitant about everything they might do because bodies might shift a tiny bit and all of a sudden a great play becomes a penalty (and suspension), not because the defender did anything wrong or intended to injure, but because of the nature of the action. Players should be penalized and possibly suspended for trying to hurt other players. However, when they're trying to make plays - hit hard, knock balls loose, remind receivers that the defense owns the middle of the field and coming in that area might result in getting knocked on their asses - and injuries, or unfortunate contact, just happens to happen, you can't punish that. Offenses have so many options - if defenses can't take some possiblities away through intimiditation, they're sitting ducks. Why would great young athletes coming up today want to play defense, when they're being told they can't play at full speed - that they can be suspended and lose money and will always have to play with 'I better hold back a little' in the back of their minds?
The surest way to get a fast moving target that is coming at you (or tangentially at you) to the ground is to deliver a powerful hit. When you just try to line them up and wrap them up, a slight move by them turns your solid wrap up into an arm tackle that might easily get broken (by a fast moving target).
Another factor is the helmets they're wearing - it seems they've gotten so good that the players have a dangerous sense of invulnerability. The natural instinct to protect they're head seems to be a bit suppressed (for both the offensive and defensive players).