
Yes, I think that it has to do with the idea that answers are different than comments, which is saying much the same thing as you were in your second-to-last paragraph. With picks and quizzes, you are unlikely to interact with the item without submitting an "answer" to the "question": choosing a pick or selecting a multiple-choice answer. This creates a bunch of stats in a user's profile, and my belief is that the staff feels that the ability to jack up those stats by manually deleting the questions would be too tempting for abuse.
That said, it may be true that you can delete Answer Requests after they've been answered. I don't know if it's true, because very, very few of all the requests I've ever submitted have been answered (I think it was you answering it, actually), so I've never tried deleting one. If it is possible, it certainly isn't consistent with my take on their thinking. I wouldn't be too upset about it if users were more inclined to use that option to delete repeat questions, opinion questions, or just really badly phrased questions (any question that asks "Does someone know X?" should be nuked - the correct answer is always "YES"). Sadly, the option may exist, but people don't use it.
That said, it may be true that you can delete Answer Requests after they've been answered. I don't know if it's true, because very, very few of all the requests I've ever submitted have been answered (I think it was you answering it, actually), so I've never tried deleting one. If it is possible, it certainly isn't consistent with my take on their thinking. I wouldn't be too upset about it if users were more inclined to use that option to delete repeat questions, opinion questions, or just really badly phrased questions (any question that asks "Does someone know X?" should be nuked - the correct answer is always "YES"). Sadly, the option may exist, but people don't use it.