Microsoft is slowly being squeezed from both sides of the market. Chromebooks have silently become wildly popular on the low end. The only advantage I see windows have is corporate and gaming. But valve is slowly chopping away at the gaming advantage as well.
Chromebooks are no where to be seen outside US school market.
Coffe shops, trains and airports in Europe? Nope, rare animal on tables.
European schools? Most countries parents buy their kids a computer, and most often it is a desktop used by the whole family, or a laptop of some kind running Windows, unless we are talking about the countries where buying Apple isn't an issue on the monthly expenses.
Popular? In Germany, the few times they get displayed on shopping mall stores, they get rountinely discounted, or bundled with something else, until finally they get rid of them.
Valve is heavily dependent on game studios producing Windows games.