There are many questions where users dont mention their Ubuntu version and ppl then ask them to add the version of Ubuntu they are using to their question so question could be answered accordingly. Why dont we make at least one version tag a must for any new question? Similar to how a question on meta must have at least one of feature-request, bug, support or discussion tag added.
I understand that there are questions which dont require version info and can be answered without it but having version info for even those questions wont harm.
There are questions that are version agnostic, where it could apply to multiple versions. Forcing version tags is a bad idea as versions then become meta tags. Currently, tagging a post with a version should only happen when that post is directly related to that release in some way. If you have problems with Apache and PHP don't tag 11.10 because it's not really 11.10 specific. It's apache and php.