Because it's descended into a frenzy of angry and spiteful circlejerking, where anyone who doesn't agree that Riot is made up entirely of incompetent idiots with their heads up their asses and that Dynamic Queue can never and will never work is either downvoted or outright insulted and demeaned.
The Gameplay Board is offering absolutely nothing positive, and I think I've even seen people outright mocking its current state right here in this board. We get it already, you don't fucking like Dynamic Queue. But not being willing to wait it out and see how Riot can improve it, just because you want your damn Solo Queue back isn't just selfish, it's incredibly immature and disrespectful. Riot is trying to make the game better for you asshats, and this is how you respond to that passion and attempt at innovation? Like a bunch of spoiled brats who can't shut the fuck up and just play the game?
....Okay, that got more ranty than it should have. But the Gameplay Board has been a cesspool for a while now, and I think it's high time Riot puts it foot down and brings and end to it.