It's currently not clear whether it's legal to even run Windows 10 Home/Pro, if you have such obligations, as even the best privacy that Microsoft allows, is still sending something to Microsoft and no one knows what it's sending.
This becomes even more fun when you consider that in order to be HIPAA-compliant, you have to always keep your software up-to-date. That means you have to upgrade from Windows 7/8 to Windows 10 and therefore can't just stick to a previous version to be legally safe.
For bigger health-care institutes, Windows 10 Enterprise might be an option here in order to not risk a lawsuit, but for a simple doctor who'd only need one or two licenses, that's not a viable option either. Maybe we'll see an organization of doctors for buying Windows 10 Enterprise License Volumes together and then sharing the licenses, but if not, they would all have to migrate to OSX or Linux.
i. Doomsday scenario: Competing platforms do something awful like direct spying on users, making it unaffordable/inaccessible or generally taking terrible, permanent decisions. Then, a free/open source OS will become The only feasible option. The counter point to this is, competition ensures very few companies will take that route.
ii. Learning & contributing: As a developer, I can understand and improve any part of the stack. Counter point: This doesn't address non-developers, who are a majority in today's world.