For sheer number, you're almost certainly right. But Microsoft products lie at the center of nearly every major company in the form of Active Directory, Exchange, Sharepoint, SQL Server, etc.
Don't get me wrong, I'm a big Linux guy and have been for a long time. If you want to build a product, Linux is definitely the way to go. But for a corporate IT platform providing applications and communications tools to business users? TCO is the name of the game; and while license costs for Microsoft products may be higher, you're going to get a lot fewer support requests because end users are capable of diagnosing and fixing far more issues on Windows/Office than Linux.
Don't get me wrong, I'm a big Linux guy and have been for a long time. If you want to build a product, Linux is definitely the way to go. But for a corporate IT platform providing applications and communications tools to business users? TCO is the name of the game; and while license costs for Microsoft products may be higher, you're going to get a lot fewer support requests because end users are capable of diagnosing and fixing far more issues on Windows/Office than Linux.