old people do this so they can read it better. That's the only people who print anything ;) ).
Have you heard about the following niches: kids, health, career, photos/pictures, management, travel, maps and many more. Print is one of the most activities in these types of sites.
Diversity of traffic sources may be the key: Search Engines can measure constant/temporary traffic volume coming from many sources, including social media networks. If this is not an effective filter to value an authority, I might have missed something.