I think what you are seeing is the ancestry of these projects coming to the fore. Ubuntu is, to my eyes, first and foremost a desktop OS that is trying to make inroads into the server OS space (replace OS with distro if if helps helps lower your pedanti-meter). RHEL/CentOS have always been very server/workstation based (and I do consider a workstation different than a desktop).
You can see this in how they focus their work. Ubuntu, while it's contributed much to the ecosystem, has focused quite a bit of those contributions to ease of use and graphical stack items. These are important, but less so to workstations (of a particular breed) and servers. Red Hat has focused on stability and management. Need a full virtualization stack? RHEL has developed a stack they are pushing as competition for VMWare. Want directory services? It's an officially supported component with documentation (as of at least 4-5 years ago). Want a bug tracker with lots of info on exactly what's going on and what to expect? Use Bugzilla. It's overkill for most user-facing projects, but for IT staff who may be expected to file a fair number of bugs over time, after you've invested some time to learn it, it's great.
Ubuntu is a great OS/distro, but I don't think they've reached the same level in the server space as RHEL yet. Similarly, I wouldn't necessarily push RHEL/CentOS for desktops for home users or most businesses needing Linux on the desktop, unless there was a need for a much more controlled environment, and the long time between versions is not an issue.
You can see this in how they focus their work. Ubuntu, while it's contributed much to the ecosystem, has focused quite a bit of those contributions to ease of use and graphical stack items. These are important, but less so to workstations (of a particular breed) and servers. Red Hat has focused on stability and management. Need a full virtualization stack? RHEL has developed a stack they are pushing as competition for VMWare. Want directory services? It's an officially supported component with documentation (as of at least 4-5 years ago). Want a bug tracker with lots of info on exactly what's going on and what to expect? Use Bugzilla. It's overkill for most user-facing projects, but for IT staff who may be expected to file a fair number of bugs over time, after you've invested some time to learn it, it's great.
Ubuntu is a great OS/distro, but I don't think they've reached the same level in the server space as RHEL yet. Similarly, I wouldn't necessarily push RHEL/CentOS for desktops for home users or most businesses needing Linux on the desktop, unless there was a need for a much more controlled environment, and the long time between versions is not an issue.