Most people would be perfectly happy with a Linux machine (I can tell you my mother is) and had hardware manufacturers given even some slight support (instead of building dozens of models seemingly designed to be Linux-proof) it would be much more popular.
The sad truth is that most people are not even aware their computers run an operating system. They believe Windows is an integral part of the machines.
The problem is that we, Linux enthusiasts, never managed to interest Microsoft's 5 most important clients (the aforementioned PC makers) on the full-featured, rock-solid, fast and stable desktop and server environment we were giving away for free.