The so-called convenience of being able to right click on a file and choose, "write to disk" has at least one huge failing: iso image files. They end up being written as a discrete file onto the CDR or DVD. This result is useless, and not what most users would be hoping for.
Why the hell would anyone want a DVD with a Spaceballs.iso file on it? Their DVD player won't be able to play it. The entire reason for the ISO9660 file system is to facilitate writing a file system to a removable disk. When you are done writing an ISO9660 image to a disk, you're supposed to be able to mount the thing, access the files it contains or even boot to it. Most users would never think to mount an ISO9660 file as a file. Windows XP can't mount an iso image without the help of a third party utility.
I ask you, why can't the OS be smart enough to see that it's being asked to burn an ISO image and then intelligently NOT stuff it into another ISO image for writing? Seems pretty obvious to me.