It's useful to shorten a frequently-used name, but not if the abbreviation is misleading.

Almost everyone in developed countries really does know that the “Windows” system is made by Microsoft, so shortening “Microsoft Windows” to “Windows” does not mislead anyone as to that system's nature and origin. Shortening “GNU/LINUX” to “Linux” does give the WRONG idea of where the system COMES from.

The question is itself misleading because GNU and Microsoft are not the same kind of thing. Microsoft is a company; GNU is an operating system.

It's useful to shorten a frequently-used name, but not if the abbreviation is misleading.

Almost everyone in developed countries really does know that the “Windows” system is made by Microsoft, so shortening “Microsoft Windows” to “Windows” does not mislead anyone as to that system's nature and origin. Shortening “GNU/Linux” to “Linux” does give the wrong idea of where the system comes from.

The question is itself misleading because GNU and Microsoft are not the same kind of thing. Microsoft is a company; GNU is an operating system.