I've troubles with the lack of a CD burnable image, too. In normal I use mint on many different old PCs, when I'm at people who like to make use of some old hardware they got, whom I want to show mint, with many them not even having a modern PC. These PCs (mostly socket 478 or socket A-Thunderbird) very often neither offer DVD capable drives, nor booting from USB at all.
As these installations often are spontaneous I usually also don't have time for creating or bringing a modified ISO in normal.
It's about once a week that I could use an ISO image fitting on a CD in between. There are many places where there could have been a happy mint user, yet