You aren't wrong in stating that they aren't worth it, but the correct way to look at them is:
You're almost done with your Mog King shopping list, and in your last or next-to-last run you get a pack of Chocobos that puts you several thousand over what you need. No one would bother grinding up another 63000 currency for the 10% moogle, but you may decide it's worth it to do another couple runs to secure the 10k for one moogle.
or
You're bad or lazy at evaluating how many runs you need to do, and you finish your shopping list while you still have to run the event for the daily quest (I do this for literally every single MK event). The leftover currency from such runs may end up around the 10k mark, so you can convert it to a moogle instead of 6* mats you don't need or whatever.
It's just an option for leftover currency conversion, not something to consciously aim for.