My guess would be that the forest of the kami doesn't care much for clothes, as they aren't 'natural'. Monkeys don't wear clothes either, and judging by how easily the women could leap between the tree branches, there seems to be some kind of back-to-primordial thing going on. Reminds me a bit about <a href="http://www.meekcomic.com/" rel="nofollow">The Meek</a> (innocently NSFW), where the main character of the first chapter runs around naked in the forest.