They are PUBLIC, that's why.
Don't they INTEND on reaching as large an audience as they can? Or are they only for a very small and very private group of people. One would ASSUME that they would go for as large an audience as they could. Jesus did.
So is your basis for mainstream media anyone trying to increase audience? Have you considered this as the mission for Barna and TGC? How could you come to that conclusion considering Barna’s status as a firm with clients who pay for the research?
Same question applies to TGC, which says it exists for current and next generation Christian leaders: why do you assign to them the goal of mere audience accumulation?
Have you considered Barna might not have lasted 30+ years in the business if it were a company that didn’t perform for its clients?