It's probably because it's what they've been using for a while, what they have figured out, and worked out in how to use it? The best ceramic is the system you have worked out, and can work with confidence with. That when you take a custom shade, or get those shade photos in, know you can get there more easily with your system and your experience with it.
You could probably find many porcelains here that people have posted and liked. Halo, Vita, Noritake, GC, etc. I'm sure there are others who use Ceramco 3, Avante who have not posted on this forum, or who aren't even members here, who get excellent results. It just comes down to what type of system and philosophy you're looking for, a translucent system, medium opacity system like Halo, or a more opacious system like Creation.