I never really thought about it, but social media taking people away from Forums makes sense, I guess. There's been a number of times when I go looking for a forum covering some vehicle. Sometimes I find only stagnate forums. When I started forums were the new modern thing. I started with mailing lists. Email to a server, that sends it on to all list members. I haven't been on a mailing list, like that, for quite some time.
I'm a bit suprised the Tahoe/Yukon forum is bigger, but I guess it covers all the years (I assume) so there's that difference.