Optionally, some people might think a truce is good for the world, because it will be better for the world if both countries have some time to prosper and create without constantly destroying stuff. But in any truce for that reason, one country is sacrificing its own war aims, and hurting its chance of winning, for the good of the world. And if that country thinks its winning the war is very important to the fate of the world, because its values are good, and the rival countries values are bad, then this kind of truce is incoherent. Sure, you get to prosper, but so too does the enemy grow stronger.
And countries are analogous to rival worldviews. Oh! And this only applies in the limit of taking your own side seriously.
Another point is, if it's say capitalists and commies, truces help capitalists, cause they have a better economy and stuff -- in peace they prosper a lot, and commies don't. Hence consistent commies should not accept peace. Nor should consistent Islamofacists. They'll only accept peace if they're confused enough to think they're the ones with the dynamic, productive society, and the capitalists are the ones on the verge of collapse, or something like that.