Feels like a Catch-22, Windows is popular because of the status quo and because it also happens to be what's taught in schools (at least over here) and what you run into in workplaces. Why? Because Windows is popular - of course you should teach it!
At the same time, modern mainstream Linux distros (think Mint, not Arch) are pretty stable and the UI/UX can be more pleasant instead of dealing with the occasional bit of Windows BS. Despite that, there are still some functionality gaps - AD and Group Policy in org settings, I would say that LibreOffice is good enough but now office stuff is being pushed into cloud (which I think sucks but oh well, people benefit a bunch from Google Docs and MS kinda just made the OneDrive/Teams/365/whatever experience be weird), as well as some Windows software just not running on Linux distros even with Wine and whatnot and sometimes there not being Linux native versions, which has gotten better in the past years.
But for a machine for a non-technical user whose mind isn't corrupted with Windows'isms and who will mostly do web browsing and cares that any downloaded files will display (videos, images, PDFs and office docs and such)... I'd say it's already a pretty good option! It's just the case that those users almost don't exist and anyone who might try to assist them will also almost always either assume Windows as the default (e.g. if they gotta call in to some support), or won't even know how to help with Linux cause of the aforementioned status quo.