There are two reasons that NFL fans like helmet-to-helmet hits. One is because NFL fans are NFL fans because they like a little bit of violence and the NFL is the healthiest way to get your violence fix. The other reason is because of things like this:
That's Raiders running back Darren McFadden and Tampa Bay Buccaneers safety Mark Barron on the ground in what looks like a passionate embrace or like the NFL has started using a new safer helmet that also happens to be made out of magnets. What actually happened was that when Barron and McFadden met head-to-head, their facemasks, got entwined and stuck to each other like Rosie O'Donnell gets stuck in (enter your own normal sized thing here).
What makes these things even better is the fact that neither player seems to ever know what is happening until they have already pushed and pulled each other for about five minutes when it's so obvious that the problem could be solved if they just calmed down and took their helmets off. Or they could always just play without helmets. Just saying.