I think a better question is why did DS9 (and subseqently Voyager) have different uniforms than TNG during the 2 seasons that they ran concurrently? Was this ever explained?
Perhaps, the DSN style uniform was being phased in, and as DSN was a new posting it got the new uniform.
I always thought of the early DS9/VOY uniform a type of fatigues to be worn in the field and it was up to the commanding officer to decide which dress code they wanted their people wearing. Though Generations got silly with people just randomly changing their uniforms from scene to scene.
That's pretty much it, IMO. They did seem more like fatigues or work coveralls. But the way they were presented in VOY made them look more like a new specific starship duty uniform that was only in service for a couple of years. I dunno. If we go with the idea of the latter uniform being fatigues the use of them makes sense if the people wearing them had to do some dirty work for awhile. I always imagined that the Enterprise-D was undergoing some major internal upgrades at the time of Generations.
So by that logic I could see the Engineering crew in them then. Maybe even the security. But literally seeing people randomly change uniforms from scene to scene was just silly. Though I guess it explains why half the lights weren't working.
This makes the most sense seeing as Sisko changes to the TNG style uniform while he's on Earth in season 4's "Homefront" & "Paradise Lost".
The running joke (as told by one of the TNG writers at a convention) was that the E-D happened to be in transition at the time of "Generations" and the crew were being issued new uniforms automatically the next time they took a shower. This is borne out when Geordi came back from being kidnapped, bathed, and he was in the new uniform. The logic sorta stops though when you realize neither Troi nor Crusher change for the whole movie. Worf stayed in his uniform the whole time, but hey, he's Klingon. It was also painfully obvious the rest of the cast were just using the available uniforms from DS9 (except for Stewart and Spiner, who had custom ones made for them). The extras in the background could be chosen to fit them, but not the principals; as a result, Riker's sleeves were way too short and had to be rolled up to disguise the fact, and LaForge's sleeves were way too long! Mark
I think it still makes sense, if we assume that parts of the fleet got the new uniforms handed out to test them in the field. The Enterprise crew, like the Rest of the fleet got the new uniforms when those were approved. Since the Uniform updates are field oriented the higher ranks from Admiral and above have no immediate need to change till the old uniform wears out.
Maybe each commander gets to choose the dress code in their command. On DS9 Sisko is in charge, so he can choose one style; but when he's on Earth he's under Layton's command, so he wears what Layton tells him to wear. Picard was obviously pretty liberal in his uniform policy (see: Troi). The various extras with the old uniforms in DS9 could be people from other ships, etc. (By the time STO rolls around, it's a free-for-all.)
The E-D uniforms durin' GEN is consistent with the series, though. When the new uniforms were introduced at the beginnin' of the third season there were still extras in the background wearin' the seasons 1 & 2 style uniforms, 'til finally everyone was wearin' the same thing.
Even after the old uniforms went away, they were never all wearing the same thing. There was the two-piece pants and shirt worn by the male main characters and some background characters, the one piece zip-in-the-back worn by the female main characters and some background characters, and the one piece zip-in-the-front worn by most background characters. Those were actually the S1/S2 uniforms altered to look like the new ones.
Different uniforms for different situations. Picard changed his because he was going into a danger planet-side; LaForge may have been expecting to do heavy maintenance work in engineering; Riker may have been down there too or doing other work below decks; and Data may have changed into the then new uniforms because nobody told him he couldn't perhaps.
Given all the other far more outlandish things that has happened in Trek since its inception, it really isn't.
Didn't they have to squeeze Frakes' frame into Avery Brooks' uniform? As far as the odd mixture of uniforms in "Generations," the sasme thing happened in TNG season three. That was sort of a transition season, with the main cast wearing new uniforms (which were slightly altered during the course of the first part of the season to eliminate the front seams) and most of the extras and background characters wearing the old first and second season uniforms.
Also worth mentioning that the notion of different Starfleet crews wearing different uniforms at the same time was nothing new either: the Antares crew in "Charlie X" wear The Cage/WNMHGB uniforms when they meet up with Kirk (who is wearing the standard Enterprise variant). IMO the best explanation is that Starfleet is just loose with the uniform code.
Yes, and it makes sense for the majority of cases. ...then, you've got stuff like, Picard critizising Ro Laren for wearing her beloved ear ring - which btw is a cultural expression. So, Worf is allowed to wear his sash but Ro isn't? ..Ok, I agree, you can say that Picard wanted to troll Ro because she was such a misfit. But are there any other cases where someone gets criticised because of things like that?