I guess I am going to get a few more of these now that I am playing 1.d4 whereas previously I have always played 1.e4 and replied to 1.d4 with 1...Nf6
My old reflexes with 1.d4 d5 are probably a bunch of old habits developed in my days of using the Stonewall attack - placing pawns on d4, e3 and f4 and guarding the e4 hole with Bd3 and Nbd2. If Black castled short you could then launch a nice attack placing Ne5 and getting queen out Qe1-h4, perhaps a bishop sac on h7.
Black is canny here and refuses to commit. Eventually castles Queen-side.