[JeremyNT]

It's the same value as Debian stable: you don't need to mess with it, and you don't need to learn anything new until the next big release.

RHEL / CentOS also has a lot of commercial software packaged and sold for it. You'll find plenty of niche market software shops that don't want to bother targeting more than one distribution, and that being the case they target RHEL. If you're writing and selling some niche business software, do you really want to dedicate your limited support resources (which, let's be honest, are probably your developers!) to supporting other distros?

At the end of the day, what do you need from the distribution itself? It's a tool to run the software you care about. Some distributions take pride in providing that software as a part of the distribution, but not RHEL. RHEL is stable, it's a known entity. You want a newer version of PHP? Go for it, but you're building and packaging your own on RHEL. And for many shops - not just enterprises - the "you" here is not actually anybody at the company, but some external vendor or some OSS project maintainer who packages everything (including dependencies) for RHEL.

And by the way, this is why Docker containers are so popular now - you can incorporate whatever system libs you want directly in your deployment bundle, and know that if the base system can run Docker you don't have to think about it. Something old and crufty like RHEL, as long as it has good Docker support (yes, arguable...) - you never need to care how old and crufty it is (they DO backport major kernel improvements to their custom kernels).