In big companies the stuff running in Windows has long been just been the Views in a multi-tiered Model-View-Controller systems architecture, whilst the data and logic sat in servers.

From my own experience, on the technical side it's mainly the sunk cost into making the custom frontends in Windows and certain apps used to fill the gaps not covered by corporate systems (for example Excel and Outlook) that have held Windows in place.

On the management side, it's probably a question of support contracts and friendly rather than professional relationships with specific Windows-only 3rd party vendors.

Not at all denying your point (which I totally agree with), just pointing out that in big enough companies to have their own software developers and proprietary systems, the movement away from Windows has been going on longer than that, just less visible to most people because what was being moved over was back and middle tier stuff.

Whilst people kept dreaming about the Year Of Linux On The Desktop, Linux had, since the 90s, quietly and steadilly been eating away at the responsabilities of software running on the Desktop.