That's the 'weird' thing with the UV editor. It starts out clean when you create a base piece of geometry but the more you model and make changes the more it becomes a giant mess in the UV editor - there's no real rhyme or reason (that I know of anyway) of why it puts the verts where it does when you add them to your model so it just turns into spaghetti and you have to use mapping to get a workable UV layout.