Because if you don't pay you are excluded, while projects that do not even make sense to exist and do not even start if they pay are considered real OS. The worst thing is that even Wikipedia does not consider them if they are not reviewed by Distrowatch. What common interests have they seen that Distrowatch is not an official body and Wikipedia claims to be free information?
Corruption is everywhere, like the stupidity of those who, without even asking, raise some private sites as open source gurus. We also consider the fact that the judge, the jury and the executioner is a physiotherapist who has a passion for tractors, not a degree in computer science.
If you're a newcomer in the Linux world, I suggest to head first to another site other than Distrowatch because there are many terms that sound kryptish if you never used Linux. Distrowatch is great as it lists almost any Linux OS out there. Besides, it lists also other operating systems. Really worth checking out.
If you are a Linux enthusiast and like to keep up with what the community is doing, then this site is perfect. I provides continual updates to the status of the different Linux offerings and allows you to in one place compare many (if not all) the flavors of Linux.
Being a Linux OS lover I find this site to be one of the most informative sites out there when it comes to Linux Operating Systems you can find just about any and all Distributions of Linux on this site. On the left hand side of the home page you will find a list of the most popular Distributions (distros) by download. You can also search for the version you want to find. Along with after clicking a distro you will be shown a page with a complete description and screenshots of the system where to download and the creator's website. The home page also shows what is new and exciting within different distros. This site is the leading site when it comes to finding that one Linux distro you have got to have
While I agree with the other reviewers comments, and this is the primary source for information about Linux flavors and packages, to my way of thinking it also sums up what, to most people, are the worst things about Linux. If you're not already a fan, you won't understand a word of it, for a start. There's no attempt to explain what it's all about, or at least if there is, there's so much other stuff on the page that I didn't find it. Secondly, there's no attempt to present the information in a pleasing way; everything is just plain text on dull brown backgrounds, as if to say, heck, we're not stylish and we're proud of it. They didn't even bother to put the name of the site at the top. Anyone wandering across this site with curiosity about Linux but little or no more knowledge than that, is never coming back unless they're already a geek. It's about time someone polished up the image, because in the minds of the public, Linux has been dull, and complicated, and for nerds only, for years.
Nevertheless, this is by no means a criticism of Linux itself. It's not a perfect operating system by a long way, but still, whoever heard anyone say, excitedly, "Wow, look, another version of Windows, must try that!"