Why user exposure matters for Linux distributions, especially on desktops
Red Hat Enterprise Linux (or equivalently CentOS) has any number of things going for it from the perspective of sysadmins, but one of things it does not have is user visibility. Ubuntu is the hot Linux distribution these days, despite its issues, with special acclaim for its desktop experience.
This user visibility matters, contrary to what some people believe (or would like to be the case).
A good part of why we run Ubuntu on our core servers is that research groups were already running Ubuntu on their machines, both desktops and compute nodes, and they wanted to us to have the same environment, partly because it was what they were already familiar with, and partly because it meant that they could easily move programs back and forth between their machines and ours. Those research groups did not select Ubuntu because they had gone through a careful technical evaluation of which Linux distribution would be better; they used Ubuntu because it had the mindshare and because it worked well enough to justify its PR.
In a nutshell, that is why user visibility matters: these decisions do get driven from the bottom up, with users advocating for what they are already using and are familiar with.
(Also, it is easier to sell something to users if it already has the visibility with them. I am sure that there would have been people asking why we weren't using Ubuntu if we'd made a different choice, and yes, their opinions matter.)
I say that user visibility especially matters on desktops because desktops are the easiest and the best place for users to get hooked on something. They're the easiest because in practice they're the machines that users have the most control over, and they're the best because they're what users use all the time.