They could, but this isn't just a technical issue it's also a legal and political issue where several AV vendors are currently suing MS in the EU for alleged anti-trust behavior. So the lawyers compromise everybody's security.
That seems like a crazy thought process. You're running software that modifies Window's internal functionality. The vendor knows it's unsupported. How can you blame the company who just made the platform you compromised?
Might as well set your root password to "password" and open it to the public then complain that the security is bad.