https://gs.statcounter.com/os-market-share/desktop/united-st...
As for market share in the US, I very much doubt it's that high really. There are huge unimaginable swathes of windows boxes which won't show up in GlobalStats at all. I know a company with 50,000 desktops that can only visit a web site on an internal network for example. Those sorts of installations are everywhere.
I already see this situation with Google, where non-technical folks will push back on choosing Google products even if they are the only credible player because of the perception that Google cancels everything and they don't want to be caught out.
Microsoft is playing with fire if they think that screwing with their customers computers will have no repercussions with other products.
Also another company we are related to tried a roll out and found they couldn't get Apple to deliver anything other than crap off the shelf configs in any quantity. Dell could. So the trial was ended.
I wouldn't draw any assumption that higher quality software is portable. I've seen monocultural genius (Keysight Genesys) and cross platform garbage (libreoffice) for example.
> because I need to do things I can’t do on macOS.
IT departments in huge corporations have purchasing requirements specs. Require any software that you pay money for to run on at least one non-Microsoft operating system. As a second source requirement.
If more than a trivial number of large corporations do this, developers make sure their software runs on other systems, which is what allows users to switch. Large IT departments are in a position to actually move the needle here.
This also has the side benefit of being a heuristic that excludes primarily low-quality software, because most higher-quality software is already portable.