Board Thread:Episode Discussion/@comment-24993958-20161231141844/@comment-28288412-20170101004703

Or they simply can't remove eachother's creations. Making something is easier than removing all traces of it again, especially if you're not the one who made it.

Sure the god of light could've counteracted the Grimm with an Anti-Grimm or straight up remove them if he could, but that would only lead to more petty squabbling and conflict.

Plus the Grimm are their own unique form of life, one that hates every other form, but still.