Actually most people use TFS at Microsoft. Some 61,777 Microsoft employees as of last month were using actively using TFS(VSO - The cloud offering of TFS).
Now the version control part of TFS is TFSVC and yes TFS does have the ability to host Git repos, but the number of Git repos at Microsoft is significantly, significantly smaller than then number of TFSVC based projects.
Microsoft as a whole "gets" the need to move to better version control tools such as Git....but the larger products will take decades to move off of the internal version control tooling for example: Windows (Perforce\Product Depo), Office (Perforce\Product Depo), SQL Server (TFVC), etc.
Now the version control part of TFS is TFSVC and yes TFS does have the ability to host Git repos, but the number of Git repos at Microsoft is significantly, significantly smaller than then number of TFSVC based projects.
http://blogs.msdn.com/b/bharry/archive/2015/06/03/team-found...
Microsoft as a whole "gets" the need to move to better version control tools such as Git....but the larger products will take decades to move off of the internal version control tooling for example: Windows (Perforce\Product Depo), Office (Perforce\Product Depo), SQL Server (TFVC), etc.