So, if you wanted a backup install disc in case something went wrong, or in case you wanted to install Mac OS X on your computer without signing into the Mac App Store, you'd have to create a bootable DVD or USB drive yourself using the InstallESD.dmg, which was an easy process using Disk Utility.
There hasn't been any physical installation DVDs available for Mac operating systems since Snow Leopard (10.6), with Lion (10.7) and Mountain Lion (10.8) both available via the Mac App Store as downloads only.