It's because splats sell a great deal better then the fluff based books. I've heard this said by several rpg publishers. The main reason given is that a group only really needs to buy one copy of DM/GM centric books for the group but player centric books, ie splats, will be something that, if good, all the players will want to buy.
Since we're wishing for things I'd like an easy to describe and use economy help guideline for DM's so that the economy in a setting would at the very least sound as if it made sense.2. Economy is a real issue. I don't wish to complicate the numbers or to make money administration a burden. I just wish players would use copper coins for the first few levels, and once they are paid in silver they are already higher lvl adventurers, with fame and glory.
Warhammer 40k? Without the Grim Dark?I'd like to see a setting rooted in the kinds of crazy world concepts you see in in old videogames and anime. Worlds where you are just as likely to see androids, laser guns, and giant floating super-technology fortresses as you would elves, wizards, and gods. Worlds where the distinctions between technology and magic or god and machine begin to blur. Places with terrain and architecture completely alien to anything seen in the real world.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.