There may be several reasons for making your own CD. Perhaps you're a cheapskate and want to save the $50 cost of the Red Hat distribution. Or, perhaps you want a distribution CD containing the latest distribution with all current updates. This is highly relevant, because after each major release of the Red Hat distribution, there have been loads of updates, several of which are security related. Just take a look at the updates/00README.errata file. A specific errata sheet also exists for each supported platform. See for example the Intel errata sheet