The answer to this question is multifaceted and, at least in the 10th Age, I've had to give it a lot of thought. Today, we're going to discuss just one of the ways in which the miracles of the gods are stymied or otherwise prevented from being panacea for the poor sap who gets his arm crushed by a falling piece of masonry. There are other ways that I limit this as well (socially, within the community of gods, and by the rigorous training needed to become a divine conduit) but this one is the most commonly applied.
Essentially, healing magic has limitations. Lower level cure spells are not capable, in the 10th Age, of doing the kinds of things that physicians are normally required to do. Since they are magic, they will heal all kinds of wounds but here are some things they can't do:
- Set broken bones
- Remove fragments of foreign bodies (arrowheads, etc.)
- Bring someone back up from below 0 (you must be stabilized and returned to 1 by mundane healing short of a cure serious wounds spell which, even then, merely returns the character to 1 and crippled, unable to receive any other healing for the day)
- Repair mangled bodyparts
Of course, we already know that cure spells do nothing for disease. There are actually a lot of cases when PCs or NPCs both would be "beyond the healing" of a simple cure spell. I allow more leeway with higher level magic as, after all, it is magic. The number of priests who can muster up higher level spellings is also exponentially smaller for each step up the ladder you go. However, by adding these simple rules, it removes the extreme utility of some cure spells and allows the setting to continue marching on in a way that is not entirely devoid of alteration (after all, you have to take into account some of the effects of curative magic now, but not all the ones that are implied by unlimited utility).
Of course, this is only if that sort of thing bothers you. Setting/rules clashes always bother me, so I strive to unite them as closely as possible.