I work at a large university. IT gave us two options for operating systems on our servers, Redhat or Windows. They also offer a DIY vmware setup. Rather than having IT manage our servers, I have to do it just so we can run Ubuntu. It is impossible to run certain packages like OpenCPU on Redhat because no one ever bothered to port it. Before you jump to the conclusion that linux is linux, it's really not. You can blame Ubuntu for going off the beaten path or Redhat for not keeping up with the times but some software packages only run on one linux distro without considerable effort. Conversely, the only supported backup solution for our servers is IBM tivoli crap and I went through hell to convert the rpm based installer into something that would work on Ubuntu LTS. IBM doesn't get that Ubuntu (or debian derived) distros are popular now either.
As a *BSD guy, I find both Ubuntu and Redhat irritating but at least ubuntu has apt-get. Funny thing is I started on Redhat 5.0 in '99 or so as my first *nix like os. Back then they had a desktop that didn't suck though.