If one of your opponents is playing green, they are almost certain to have more lands in play than you
If for some reason you need to keep Fasting around, your opponent(s) can force you to draw a card, killing Fasting
While you can tune engines to draw extra cards and control the game, some tactics are simply more consistent (bunnies can easily overwhelm an opponent, for example, thanks in part to the new Offspring mechanic)
Scuttletide While most delirium cards arent worth much without the mechanic enabled, Scuttletide has no such requirements
Klothys, God of Destiny I enjoy slow graveyard interaction like Deathbonnet Hulk over massive hate like Bojuka Bog, and Klothys, God of Destiny is more in that slow interaction space