Of course I know all that. Until Linux came along, GNU consisted only of a bunch of UNIX tools and a partially completed kernel. These tools, without their own kernel, became very popular in all UNIX distributions. GCC, for example, is the standard for Linux, the BSDs and OS X, and ships with at least AIX, Solaris and HP-UX. That covers most of of the 'nix market, hardly "not much".
Where would you prefer to use Unix, specifically Solaris or OSX?
If I have a choice, I use software by merit and applicability to the role in that situation, not by loyalty. About the only thing I wouldn't do is buy SCO's offerings because I don't want a dime of my money going to a company that slimy.
Why are you supporting Stallman endlessly, when these other choices exist?
I correct factual errors and counter anti-OSS zealotry. And those other choices cost money and limit the freedom to tinker.
So you can't name a single time you'd use an actual Unix like Solaris or OSX over one of Stallman's clones. Exactly what I expected.