Uh... what?

Lots of big hits happen on the line, both associated with tackles and not (a “pulling” offensive lineman hitting a defensive lineman or linebacker coming through an apparently open lane being a prime place big, non-tackle hits occur.)

Now, it may be true that because linemen are—compared to, e.g., wide recievers—built like tanks they visibly respond differently to the impacts (but that just means that something cumulatively bad for the brain won't be as likely to be limited by other more acute injuries), and it's definitely true that a lot of those impacts happen off the ball or as the play goes by, and so aren't as much a focus of attention and camera priority.