Isn't this said when you very much DO know what you want, but you have been saying all year "oh, I really like that XXXX" or when you have a hobby and repeatedly say "what I could do with is a XXXX", and then two days before Christmas you get the "what do you want for Christmas?" question?
And you think "if you only listened to me when I'm speaking, rather than pretend-nod along whilst thinking about your own stuff - you'd know?"
Just some abstract musing; I've had a lovely Christmas but was thinking back to past partners, none of whom seemed to listen to anything I said, and then seemed surprised when they weren't given a list of instructions as to what to buy me? Because, given the amount I go on about things I like and need, I kind of assumed they'd know?