I think the reason you've not seen anything typeset that way before is because it's ridiculous to do it that way! You end up with an awful mix of fully justifie

I think the reason you've not seen anything typeset that way before is because it's ridiculous to do it that way! You end up with an awful mix of fully justified and ragged-right... to my eye this makes me expect new paragraphs where there are none, for example. It's such a shame that Amazon just doesn't seem to care about good typesetting practice. It's maybe just not something Amazon views as a "barrier to sale", but as Gruber says, the Kindle only has to do one thing well, so why shouldn't it do it fantastically well?