Sibling Axes

I was reading the thread "multiple XML tags -> single output" and I came
across an interesting question. Why are there preceding-sibling and
following-sibling axes but not sibling or sibling-or-self axes. Is it simply
because you can accomplish the same thing by using ../foo or parent::/*/foo
or is there another reason. 

Just a thought.

> 		Adam van den Hoven
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