Comment 4 for bug 464601

Thank you for bringing this bug to our attention. However, a paper cut should be a small usability issue, in the default Ubuntu 9.10 install, that affects many people and is quick and easy to fix. So this bug can't be addressed as part of this project.

- This was never a problem in karmic nor will this likely be a problem in stable releases, Which will usually be having the latest versions. And changing the update policy is not a papercut issue.
For further information about papercuts criteria, please read https://wiki.ubuntu.com/PaperCut.

This is done to maintain the stability of the release and not to expose the stable releases to any unknown bugs.
You mention IE updates in windows , but you also need to remember that with every update there were several users who said that the IE update broke the web pages or there were other problems. There were even several mentions on the web to not install the immediate update of the IE8 as there were problems. this has negative impact on the stability of the OS.
 This policy is to maintain that none of these problems arise in Ubuntu.
But, I agree that when an user explicitly selects the new version the preferred app also can be changed , the you could bring up such discussion in the desktop mailing list > https://lists.ubuntu.com/mailman/listinfo/ubuntu-desktop
You can read more about the update policy > https://wiki.ubuntu.com/StableReleaseUpdates

To prevent your problem where the uri opens with firefox 3 , you can change the default web browser to firefox 3.5 [or shiretoko]from the System > Preferences> Preferred applications menu.