Because MS wanted to cram in all the DLC before the next generation launches, people no longer have much of a reason to stick it out for the game. Besides, y'know, actually playing it and enjoying it. Weren't there Halo 2 map packs launching well into... holy crap, 2007?! Wow. That [i]is[/i] late, I had no idea.
inb4its because the game sucks
inb4opcantinb4
inb4inb4opcantinb4 maybe.
I should point out that H4 was my personal GotY 2012, but it didn't have much competition. Trials Evolution was the other frontrunner.
-
I love H4's story, even if they changed/twisted some of the already established canon to tell it. The multiplayer was shite though.