Dominion needs to be eSport.

Out of the 4 maps in the game, it's the most exciting to spectate. There is always something big happening somewhere on the map. From the second the gate opens, it's pure PvP action. Compare that to SR where you MAYBE get 1 early teamfight over jungle invade security, then sit for 30 minutes in lanes PvE where a ward kill can somehow be the high point of the action. In Dominion, there's always an opportunity for a comeback. On SR, the rich get richer, snowballing any advantage into a game win, after dragging it out for another 40 minutes of one-sided gameplay.

So why has Riot not hosted anything themselves? The DD community made an excellent show of it, but Riot has the further reaching audience and would attract tons of views and enough attention and players to the map to sustain ranked. Even starting as a small tournament run and streamed between other LCS matches, it would generate a ton of interest, and likely prove to be the high point of the stream.