The software giant is trying to build a business model on selling additional content for games and it looks like they don't want game publishers to release stuff for free:
We already released two (maps) and we have four more maps that we've built. We've been wanting to give them but actually Microsoft has been pushing back on us. They're trying to build this business model around selling additional content for games and that's a valid idea, but we would definitely like to release more stuff for free, and we haven't been able to do so yet.That's really lame from Microsoft.