Personally, I never understood why they used the Deep Space Nine uniforms in Generations. It just doesn't make any sense at all. Every time we were shown non-DS9 personnel in DS9 prior to the First Contact/Dominion War uniform, they wore the TNG uniforms. Hell, Sisko changed uniforms in that Paradise Lost arc.
My guess is that they still wanted some sort of 'uniform-recognition' with TNG.