This was made clear by the Artist Job Sheet for the 15 June session, as reproduced in the media-carrying book of The Cutting Edge 1965-1966, Deluxe Edition. See the box headed BUDGET ALLOCATION.  At the time the session was booked, Columbia (and Tom Wilson in particular) probably thought Dylan already had his next single ready to go, in the shape of "If You Gotta Go, Go Now"; so the priority was to work on the next album.