I frequent the 64 boards (usually reading, not posting), but quite a few of the LA 64 players do not. Tbh, some of them just don't enjoy it. I would daresay that some have been treated not so well there before.
Uncle Kenny posted a Mario video he wanted critiqued there (recently, might I add) and I don't think anyone ever responded to it. While it wasn't harsh, that lack of recognition probably doesn't make him want to try posting another video for critique. I personally would prefer harsh critique to being ignored.