Why is GNU/Linux Market share so tiny?

GNU/Linux or simply Linux has been around for two decades almost. A good 10 years ago, I read of it in a Computer magazine as the fastest growing OS. Over the years, I have seen numerous newsfeeds, blogposts, magazine reviews, Technical documents, Text books and still even after so many years all of them state about Linux being the "fastest growing" OS. Thousands of implementations worldwide, most of the big Fortune companies using it in their env, millons of downloads by desktop users and still only "growing"? And the market size of 2% in the desktop, I wonder why is Linux so understated. At this time, I agree that in the Server and mobile phone market it has sizeable presence. So going back to the desktop marketshare question--why is Linux so small in the map? When will it be really considered as "Grown up" instead of just "growing"?
Well, here are my thoughts on this. I think the numbers are misleading. In my experience and written sources all around the web, I think the Linux Desktop marketshare is more than just 2%; probably atleast 10%. May be even more. The main reason I think is embedded in the nature of Open source software and how they are distributed. Open source allows you to run, modify, copy and share your software as long as you pass on all the privileges that you received. This means, the count of Linux downloads from various repositories and mirrors are only the start. There is no real way of keeping a track of the subsequent copies of the software that get created. My own example is worth considering. I have 6 computers at home. All but one run Linux. And they have been installed from the same Linux install disk that I downloaded originally from the Internet. So if you were to consider the the install size only on the basis of download, I will have 1 install, where as in reality I have 5 installs. In other words, there is no account of 80% of the Linux install base in my own case. Therefore the download count does not serve as a reliable source of information. And this I am sure happens all the time will all the Linux users. Since the GNU GPL and Open source licenses have no objection to users creating multiple copies and installs of their single source media, the actual install base is much larger than the reported. At least 5 times more.
The next problem in counting Linux desktop installs is the enormous numbers of variants for Linux available. There is no real count of how many flavors available or possible at any given point of time. Anyone can modify the source code and create a new fork of the Linux OS. And it gets done over and over again, in each of those repositories. Example: Red hat has lead to Fedora, CentOS, Oracle Linux  etc. So the count of install base of each one of the flavors is nearly impossible.
That said, I think Linux still has a big way to go. It needs to grow bigger, much bigger than it is now which in real terms is 10%. It needs to realize its real potential and have its userbase size to grow as the largest desktop OS in the history of humankind. It is possible. It will happen. The folks at FSF, Opensource, Canonical etc are doing a tremendous job. Others need to join in. It is only a matter of Time now.