It is unrealistic for distributors to ship pristine upstream, always. Upstream and the distributors are not synchronized (and don't anyone mention the idea of synchronicity), and might also have different priorities about which patches to include since the last release or not.
Over the lifetime of a distribution, only selective backports are feasible, and the priority will be given to bugs reported by or affecting paying customers, or security. That a CentOS user has no pull with RHT should not really strike anyone as surprising.
Users who want sources which include the most recent bugfixes and upstream code should follow the Raw Hide or Factory versions. If you're running CentOS, RHEL, SLES, you are expecting something stable and "mature", that is to say: better the devil you know than unexpected regressions. If that's not what you want, chose differently.