In the first alphabets, the letters didn't have a particular orientation. There was even this strange (to us) writing system of writing every other line as a mirror image. http://en.wikipedia.org/wiki/Boustrophedon
Wow, that actually seems more sensible than our style. It would save time scanning back to the beginning of the next line, and it would make it harder to end up on the wrong line, since different lines would be going different directions.
