See here for a full summary, but basically the most ancient empire in the world ran on chaos (essentially using it as a form of fusion power to run ships and power weapons), but eventually fell due to their technology failing and Order became ascendant. Order and Chaos traded ascendancy for a while, and we find out partway through the series that the Balance works to keep things balanced, so the more chaos there is in the world the more order there is as well and every "chaos focus" (extremely powerful chaos mage) is balanced by the rise of an "order focus."
The order forces develop ships running on chaos-engines contained by order-hardened iron, dramatically increasing the amount of both order and chaos in the world, and in fact they are deliberately increasing the amount of chaos in the world available to their enemies in the hopes of strengthening themselves, because most of the order is concentrated in one group while the chaos mages are widely dispersed. The cycle keeps escalating until it gets so bad that the druids have to pretty much wipe out most of the world's order and chaos to prevent Bad Things from happening.
Combining that with your suggesting, to make Law and Chaos conserved quantities as much as Good and Evil, would actually explain a lot. The Blood War, why magic items are stored in dungeons, the way villains seem to keep coming back unabated, why BoED and BoVD work the way they do, and more. I'll probably use something along those lines from now on.