Google is getting in to the OS business. I suspect this is as much about dogfood as security, but hammering on security is instant bad press for Microsoft.
Well Google is also competing with Apple's OS business. The bigger point is that Windows doesn't offer users any advantage over Linux or OS X anymore. Its not like the old days when Windows had the most applications and driver support.
The number of games supported on Windows is much better than for Mac/Linux.
In the context of Google, that is not a criteria.
.. and that is one more reason for corporates to move to Mac/Linux