From OXCGN:
"Thank you Epic.
Thank you for the effort and intelligence to work out to bring back the bots to both online and offline multiplayer with Gears of War 2.
Since Perfect Dark Zero bots have gone missing this generation on the 360, with only Live Arcade titles like the simple but enjoyable Age of Booty integrating AI as opponents into games.
The focus this generation has been squarely on finding Live online 'community' members in lobbies or on friend's lists to play against in multiplayer and owning Gold Live membership."
A list of reasons why Gears 2 bots rule after the link: