Think if its a "drop the hand from the neck and pose for the camera" kind of stance then i'm with you and agree it just looks naff.
However if its to adjust your amp or scratch yourself (but not your bum or intimate areas.....or anyone else's for that matter) then its probably acceptable.
I try not to make it obvious i'm doing very little and would rather keep both hands on bass unless its a crowd involvement section to assist in the clapping of hands.
Dave