Its a really good question and it would be excellent to have a rep from every brand on here. But you have to look at the amount of S*it that Epic and Dimitri has to put up with on a near daily basis. Why would anyone want or need to bother with that if you have a direct link on your website?
I have asked this very same question when I first joined the forum
Last year I was at a demo day and there was a brand rep there, who I asked did he use the forums. His answer was " he monitors them just to see whats going on but would never join them as there are to many people out there that think Trolling is fun and you can not win and argument with someone like that.
Also I think the world of Kitesurfing is still very small and so any bad blood between companies shows itself on here.