I don't know that I'd classify it "segregationist". I think it's more a matter of people having only so much time. Therefore, they tend to gravitate toward those threads that pique their interests.
For example, let's say that I log on, knowing I only have about 15 minutes before I have to go run an errand (or whatever). If I see one thread that's discussing a product that I have or am considering, and another thread discussing something that I don't own or even care about, which one do you think I'm going to open up? Of course I'd go for the one I "know" to see if somebody has something helpful, OR critical to say about it. Because to ME, that's what's interesting at that time. Like anything else in life, we have to set priorities; so if time is a factor, most of us will click on that which catches our attention.
When time is not a limiting factor, I'll look at any thread, just in the HOPE that I'll find something interesting, helpful, or just plain entertaining.