There are quite a few questions about behavior that confounds a user, that turns out to be resolved by cache clears. Frequently they don't get or need an answer beyond that. Should these be closed? Should there be a reminder on the ask page to clear caches before asking?
Questions are closed for specific reasons, and (generally speaking) the fact the answer for two different question is the same doesn't make the questions automatically duplicates. A question about
hook_form_alter() can barely be considered a duplicate of a question about
What can be done is creating a canonical question about a topic, and eventually closing any question about not recognized hooks for which the answer is "clean the cache."
For example, the canonical question could be:
I am developing a module, but for some reason the hooks I add are not recognized by Drupal. What am I doing wrong? Is there anything I am missing?
The answer would be that Drupal caches the list of hooks implemented by a module, and that when editing an enabled module causes Drupal not to notice the newly added hooks. The answer should then explain what to do in such cases.
After that canonical question is created, the other questions could be closed as duplicates, except in the case the OP clearly states s/he cleared the cache, or enabled and disabled the module, and that didn't work.