If that was the only problem though we would have expected FreeBSD to overtake the desktop. the larger issue, unfortunately is just that people are afraid to switch from Windows to anything other than Mac. Android is helping there, but it will take time.
Never underestimate the fear of the consumer that they will break stuff on a computer they are unfamiliar with. The fact that Windows is actually getting better may actually be a good thing regarding other possibilities of desktop software.
As a FreeBSD user since 2007 I found the desktop options to be just as clunky as Linux if not more so. It was the only part of the OS that didn't just work when I used it in my travels, so it's stayed as server duty. If there was an open source windows managing system that was on par with Mac's version...whole new world. (There might be, I havnet' looked since 2009 so)
Never underestimate the fear of the consumer that they will break stuff on a computer they are unfamiliar with. The fact that Windows is actually getting better may actually be a good thing regarding other possibilities of desktop software.