Require documentation update for any new feature

It has been a while since we introduced a new documentation structure for modules. Some main modules have been updated and it works pretty well to answer support questions so far.
But there are still many modules that are not yet updated and I do not see any trends in this way.

So I would like to enforce that to add a new feature to a module (no matter the size), the documentation of this module must be updated to the new structure.
This can be done in a separate merge request (preferred) or in the same merge request (as separate commit).
For this update, it is not mandatory to include usage.rst as this is usually filled over time when frequent questions are asked on the forum.

Here is an example of such update: Update documentation of stock package shipping UPS (3735e6359ce4) · Commits · Tryton / Tryton · GitLab

What are the reasonings to skip such new rule on some changes?

Here are two examples I found:

Fill free to write the documentation.

This is the task of who adds the new feature, isn’t it?

My concers is why do we need to have rules if they are not enforced?