They put their OS in most prebuilt computers, which unlike Apple are mostly affordable for the average user, so it's what people are used to. Linux is a lot of DIY even with user-friendly distros, and I think the tech support they give isn't as trusted as Microsoft's.
I have been trying to get far from GAFAM but, due to how shit is already built around it, it's hard. I don't think I'll convince anyone to give up whatsapp at all, let alone Windows
Awwwww :(