: Why would someone invest in a phone or OS upgrade just for one arcade game?
: Sounds like you're buying a house so you can bake a cake.

I think the idea is for it to be one reason among others, like another straw on the camel's back, and hopefully one of them will make people buy the OS... and break their back, I guess? This metaphor is like herding cats with broken legs.

: Make it exclusive for a bit or whatever, but logically, almost all Halo fans
: own XBoxes - why wouldn't you want to sell your game to your widest
: audience, at some point at least?

That's their widest present audience, the potential audience of PC, tablet, and phone players is much bigger. Anyway they know they still mostly have a stranglehold on the OS market; if you want to get anything done, especially with other people, it's a safe bet you'll upgrade Windows, if not to the next version then the version after that when it comes out, and then maybe you'll get the game-- the chances are pretty good with it being $7.