Wasn't Kubrick a noted fan of Academy Ratio though? I'd heard that he was very distraught over what happened to the composition of 2001 when it was cropped for TV, and that certainly would be one reason for him to go with 1.37:1, but I also think I read that he preferred Academy Ratio in the first place.

Kubrick definitely composed his shots with both 1.85:1 and 1.37:1 (roughly equivalent to 4:3) in mind, but I think he focused on 1.37:1 more. I remember thinking how cropped the image looked when I went to see Eyes Wide Shut in the theater. The DVD presentation is much better (side note: grab the uncensored UK version if your DVD player is multi-region capable).