I think it was one of those "bad planning" things. You know, finish the worms and snakes and realise you've got a jumbo box of legs left, so the things that were supposed to have a civilised number of legs (like four) wound up with eight. And of course you have to USE them all, because of quotas, so there's no slacking off. At the same time, you've only got so many bodies, so there's no getting around it. You've just created something that careens around on eight legs, looking like it owns the world because it has all these damn legs.
...I think I just equated the creator of the universe to Soviet automobile manufacture.