The other thing I find odd about the film is the desirability of the apartment itself. After all, New York City in 1960 must've had hundreds of hotels where "Mr and Mrs Smith" could check into for an hour or two with no questions asked. Certainly, it's nice to pocket the $5 (or whatever it was in 1960s play money), but it's never even mentioned as an alternative to be dismissed except at the very end, where MacMurray points out the impossibility of getting a hotel room on New Year's Eve. Is it just that "nice girls" in 1960 simply didn't go to motels with married men, but would go to a man's apartment? At least one of the philanderers lies and calls it his mother's place, but another is quite upfront about having borrowed from "some zhlub".