It's not their business, it doesn't make them money. They don't need to be competitive. They do what they need to do to protect their users (from clogging their hotline). I don't mean to say they do poor AV on purpose (or that it's poor in the first place). They just don't invest that much in it and as a result the protection is on a different level when compared to other major AVs.
> It's not their business, it doesn't make them money.
They used to think this. They got such bad press for a buggy, exploitable OS that it cost them quite a lot.
> They don't need to be competitive.
The OS needs to be competitive, and I think you're mistaken if you think the AV team at MS doesn't work tightly with the OS team, if they're in fact different.
> They just don't invest that much in it and as a result the protection is on a different level when compared to other major AVs.
At a different level because they don't put a bunch of crap on top of the OS which in most cases is really just a placebo? MS running a traditional AV division would be the height of stupidity. They are the OS vendors. Their fixes should be structural, not scaffolding.