Pretty much every template worth its salt has documentation, and those that don't generally need it.
Why do we have to use [[Template:Documentation]] to use this ubiquitous feature? Transclude it automatically.
There was a Wikipedia discussion on the matter which can be found at the following link. There was clear consensus, but the roadblock was "the proposal calls for non-trivial and not-already-done development work". Can we whip something up so that it can be implemented properly?
But realistically, how many templates are to be found that happen to end in '/doc', paired with other templates of the same name sans /doc, which aren't intended to document one another?
This can furthermore be viewed as part of the progress of template documentation, which I believe will (or ought to) eventually result in a separate namespace for templates' and/or other pages' documentations, further reducing the concern of coincidentally named pages. Further discussion on that matter is required though.