It does, but hardly anybody makes use of it - you
either get a document
containing only scanned pages (and possibly some form of contents menu),
document containing "plain text" where the
original scans have been thrown
away. It's very rare that the two are seen combined, presumably because
outside of the context of historical preservation there's no real
justification to do so; in those cases the raw content itself is more
important than how it's actually arranged.
It depends of who uses it. I use the adobe acrobat suite and try to scan
AND ocr every document, to preserve formatting and text search abilities.
Most (well?) scanned books I see on the net uses this feature, it is just a
matter of standarization. Just like rippers try to rip tv shows into a
standard format/resolution/bitrate, there should be any way of creating a
standard for scanning docs and books. There are many things that needs to be
shared on the net and still are in paper.