The thing is:
Most of the packages on the original DVD/CD's are outdated soon after it was released, you can install off the disc but as soon as you check for updates, most of those packages have a newer version and you'll end up downloading them as "updates" anyway. So this is why the discs are not configured as a repo, the strategy is "if you're going to download anyway, just tell yum what to install and it will download the updated package and install the latest", easier to avoid package conflicts this way because of the different repos due to licencing issues like "Extras, Core, Livna, etc.".
If you absolutely need the disc as a repo, here is one link that should help:
http://www.linuxquestions.org/questi...d.php?t=537641