I remember being in college and seeing the start of forums dedicated to a sport or hobby. That's how college paintball grew b/c first there was a forum just for college teams. Google just accelerated this as it made them easier to find. That then got eclipsed by BIG dedicated forums like PBNation.com (with a dedicated college forum) and then it went to FB.

That "if I just browse around, I'll find the nexus of what I'm into" seems to not be a thing for teenagers these days.