I would say very many businesses these days use Google Docs, which is compatible with every OS. That's the way we are actually progressing here; everything is multiplatform.

How many mainframes run windows? It doesn't matter, because mainframes are not where the computing mainstream is.

The typical computing customer today would have no idea what Postfix or Libre Office are, nor would they know what Azure is. The whole issue of what matters has shifted out from under those things.