Earlier quoted context omitted.
It seems we have different assumptions we're basing our arguments on. I get the impression that the huge diversity of linux distros is enabled primarily by the fact that more and more development these days is web and not native.
There isn't any great diversity in Linux distros interface-wise. You basically have a handful of distros that use X Windows and one of the four old window managers.
But we haven't even considered BSD-flavor. Perhaps if we expanded to include BSD-based operating systems. To name a few: FreeBSD, DragonFly BSD, PcBSD, NetBSD, OpenBSD.
All of the BSDs mentioned above have a very unique mission.
It's easier for me (as consumer) to choose any one of those to run my desktop / laptop knowing that I'm going to pretty much get all the same access to apps that I would if I were to run Windows or OS X.
Without any reassurance that I'm going to be able to do what I need to do on a BSD or Linux machine, I'm probably going to be stuck choosing something created and maintained by Microsoft or Apple.