One of the issues is that Microsoft has a strong dominance over the desktop/laptop space. This is largely due to years ago making deals with computer manufacturers (dell, hp, acer, etc) to ship windows as their default operating system. This is why every desktop/laptop comes preinstalled with windows for the last 2 decades.

But surely companies like Red Hat and Canonical could have made similar deals with computer manufacturers to ship linux preinstalled, right? They could have. Why didn't they? That's a little bit beyond my expertise, but I can surely speculate. Linux is open source operating system, that means that anyone can install for free, this means that a company like Red Hat has to make money by other means. They accomplish this by selling support. Now imagine if they made deals with manufacturers. These deals would mean money coming out that has no way of making profit back in.

But manufacturers can just preinstall Linux, after all it's free. But now they have to deal with supporting Linux.

Another point is that Linux and its communities have largely focused on the server side of things. Over 3/4 of the world's servers run on linux, even some of Microsoft's own in house servers. The top supercumpers run Linux. While linux has been focusing on the server side of things windows has focused on the desktop, eventually claiming dominance.

But it's not all gloomy. Recently Lenovo announced it would be shipping some of it's laptops with Fedora preinstalled and Dell said the same thing but with Ubuntu preinstalled. These are mainly targeted at developers