I suppose it is difficult for a necromancer to function in an environment like this. However, there are a few applications that don't necessitate the use of whole corpses.

Remember that everything is composed of the various Maians, where there are also requisite materials for certain spells to be cast. It's entirely possible to infuse Sakra and Karma into things like blood or bone dust, themselves integrated into rocks to symbolize a "body". It's one of those symbolic style magic things. As a matter of fact, as Necromancy [i]doesn't[/i] directly deal with spirits, it's actually the practice of utilizing things that are attuned to carrying spirits, but have had the spirits vacate them. It isn't that you're slapping a spirit into a skeleton or a corpse, but you're injecting new energies into the vacant room left behind.

It's also entirely possible that a Magestrava skilled enough in Necromancy would be quite a capable healer and physician. Necromancy is a profession of life, death, and undeath, after all. They're the world's best at recycling decayed and dead material.

Though I do agree that it'd be interesting to summon coffins from the ground :P. I can see a very interesting twist on that if you know the history of a certain field that happened to host various battles, or some kind of massacre. Anyway, just giving some food for thought!