Because then there's one big enemy we can gang up on instead of a million little ones that scatter like roaches.
Is it better to have a few "authoritative" sources everyone believes that exhort us all to do something stupid, like Vietnam or Iraq, and we trust them, and we do it with minimal-to-no hesitation? Or, is it better to have a million little squabbling social-media echo chambers and gridlock?
So far, I think I prefer the latter.