If you are a commercial software developer, you would like an operating system where security risks (e.g., viruses) discourage users from pirating your software.
Yes, there's a limit to what users will tolerate. A system that is too insecure would not work. But the virus threat needs to be real to discourage piracy.
Ultimately, users do care about an OS with lots of software available. Many users will put up with some security threats to get that.