The decision to skip the Detroit show makes good sense on Nissan's part: they just unveiled all of their new or significantly redesigned cars at the Los Angeles Auto Show in November (including the 370Z, the Cube and the Infiniti G37 convertible). With no major reveals in store, the expense of the show wasn't justifiable.
Nissan's dealers were willing to foot their own expenses to show up at Cobo Center anyway, but Nissan issued a request that indicates other motives could lay behind the absence from Detroit. Owner of Ann Arbor Nissan and co-chairman of the Detroit Show, Doug Fox, told the Detroit Free Press, "They just said they had made a national decision not to participate in this show and they asked us to respect that."
Why they made that national decision - if not for budgetary reasons alone - isn't yet clear. Nissan hasn't commented on the issue and isn't expected to.
Nissan's next auto show appearance will now be the Chicago Auto Show, which the carmaker had also previously planned to skip, but later reversed that decision.