That's a great question! I believe it is to make the person feel good almost as a micro compliment and then break out the bad news
That's a great question! I think it's for the same reason as why people ask you how are you even when they obviously don't give a single fuck about it. It's just a customary opening phrase
Wow! Great question. Let me take a step back and think about that. But seriously I think you are missing the forest from the tree. I think the bigger question is why are they not saying " amazing question ".
That means that every other question was not great.
It's to buy time, and also probably means that the question was unique and unexpected so they don't have a canned easy answer. So yes, if someone has to spend some time thinking of an answer, then maybe it is really a great question. No need to be cynical about it.
It's said for mundane, obvious questions.
This is a bad question. Since this is a bad question which contradict to your hypothesis that every question is great, this is a bad question.
Wtf I was thinking this 2 hours ago...srsly wtf
I find that most of the times I have said this, what I actually meant was “I’m glad you asked that question”
Buying time, it's a classic tactic.