@Ocular Sinister. Experience tells me otherwise
When Dapper Drake (6.06) was the LTS release, by the time Hardy Heron (8.04) came along, many of the packages in the repository were functionally stable. This meant that you may get bug fixes, but you would probably not get a bump of the version.
If you were adventurous, you could add the 'backports' repository to the list of subscriptions, and get a select few packages at the same level as a more recent Ubuntu release.
As a result, even though dapper was still 'supported', it began to be very difficult to put .deb files from the Debian repository onto Dapper, because the prerequisite libraries would not be present. Ditto compiling up stuff from source.
Hardy does not appear to be quite so prone to this, now Lucid is available, but you can see it starting to happen, especially with third-party software like the BBC iPlayer.
I'm sure that if you joined the Ubuntu developer community, offering to make the backports repository more complete, you would be welcomed with open arms. But until then, the current developer community will be more interested in putting recent versions of the packages into the latest-and-greatest releases, not into the older ones. I myself would love to do this, but personal commitments do not leave me with the time to do it at the moment.
It's a shame, as I believe that ordinary users would be best served putting a LTS release on their systems and leaving it there for the lifetime of the system.
Strangely enough, I did a Windows XP to Windows 7 upgrade recently (one of my kids gaming rigs), and it was much easier than I expected, at least using a second disk and a parallel Windows 7 retail install to make a dual booting system. I do not think I had to re-license anything. All the programs installed on the XP drive were identified and recognised, and ran without problems. But these were mostly games, but did include Office.
Microsoft must be doing something right!