This is somewhat similar to "Your answer is in another castle", at least from a searchability standpoint. Without descriptive text that summarizes or restates the actions described in the animated GIF, there is nothing that a search engine can do to "grok" or index the answer.
Additionally, this type of answer suffers from lack of ability to be automatically translated into other languages. Even as poor as some automatic translations are, sometimes key nouns or verbs are all that's needed to get the point across.
Finally, this sucks from a disability/usability standpoint. Now, it's certainly arguable that a site that is dedicated to visual media is discriminatory against the visually impaired by its very nature. But that doesn't mean that the information about how photography is done, its tools, processes, etc., needs to be locked into non-verbal or visual-only dissemination methods.
Stack Exchange is an exercise in crowdsourced search engine optimization (SEO). Information that is exclusively, or even primarily, locked in animated GIFs is the very opposite of SEO.