There's also the issue that, in order to repair, you need Dark Matter, and because there's five different grades of Dark Matter you need to to sacrifice five inventory slots to carry the stuff around with you for repairs. The fact that Dark Matter itself costs gil means that the amount you save by repairing your own gear is even smaller than you'd think.

The combination of all these - hassle on changing to a new job, lost inventory slots, and the fact that only a tiny amount of gil is actually saved - is why I gave up on the repair system a long time ago. It's just not worth it - and this is coming from someone who's ridiculously stingy in most other regards.