My understanding is that a lot of serrated blades we see from history were decorative in nature. There are some famous straight bladed two-handed swords from Europe that also have partly serrated blades, and they were definitely decorative. Also that first one you've got there is clearly designed to look like a snake in addition to the serration. Style over substance, basically. In practice, if you were to use one, all those serrations would do is either get caught in your opponent, leaving you vulnerable while you tried to extract it, or probably more likely caught on your opponent in some way; their gear, etc.
Also... could you imagine trying to sharpen a serrated blade? What a pain in the neck :)