I recently realized that even though Ubuntu LTS is receiving 5 years of support, a lot of the packages in Ubuntu LTS package repository are not updated with the latest stable releases.

For example, `php5` package in Lucid (10.04 LTS) is at [5.3.2-1ubuntu4.17](http://packages.ubuntu.com/lucid/php/php5); while the same `php5` package in Precise (12.04 LTS) is at [5.3.10-1ubuntu3.2](http://packages.ubuntu.com/precise/php/php5).

Why the discrepancies? Update one while not updating the other despite an Ubuntu release is still being supported?

And, what are the package update policies as to whether to update a package or not.