Question and Answer is a bit different from a quiz. Because for a quiz, we would want automatic evaluation of answers which doesn't allow passage answers. So we want to keep a tag of question types, store answers etc, allow creation of tests by selecting questions satisfying the requirements, provide a quiz UI, do evaluation, provide a result page etc. This can never be a core part of Q2A because then it's not Q2A but can surely be implemented as a plugin. On our site we do make use of such a plugin.