Because this is ridiculously fun compared to League of Legends (or D3)
After playing diablo 3 for a few weeks (ie, until I got bored), I moved on to League of Legends, because the gameplay is exactly the same as D3. Just spent 6 or so hours choosing random chars, walking over to my lane, waiting 20 minutes for things to get interesting...and then I re-installed this game.
Then I played a couple of single player skirmishes, and had a great time. Does anyone play multiplayer anymore?!