Does anyone know the reason for the alternate Captain's uniforms? Kirk had the wrap around in the original series and several wardrobes in TMP and Picard had the open jacket in TNG and the waistcoat in the film. From memory the change in Kirk's uniform's in TMP was to show time passing but was there a reason for the other alternate uniforms? And why did Sisko and Janeway not have alternates?
A real-world reason may be to better visually distinguish the show's captain from the rest of the cast. "In-universe" might be simply to allow captains a small luxury from the non-stop demands of command. Sisko's later uniform (post-"First Contact") was slightly different from the others in the sense that it was two piece and featured a vest underneath like Picard's. It probably became a casual when the jacket was removed, IMO. Janeway might have had a "captain's casual" uniform as well, but simply chose not to wear it (at least not in any episode we saw) as such a uniform was likely an optional one. Then again, those early uniforms we saw on DS9 might have been considered a casual uniform anyway.
I thought as much on both accounts. I was hoping there would be a more interesting reasoning behind it but alas just the obvious.
I thought I remembered an episode of D.S.9., perhaps early on, where Sisko wore (maybe breifly) an open jacket uniform.
I believe the wraparound shirt was originally to distinguish good-Kirk and bad-Kirk in "The Enemy Within." There weren't any "captains only" uniforms in TMP, there were just a lot of variations of uniforms in general.
Just finish watching the Matrix trilogy again, noticed that all the hover ship's captains wore purple sweaters, and none of their crews did.
The better question is why are hot chicks free from a dress code, and get to dress in super skin tight clothing all the time.
As J.T.B. mentioned, it's reasonable to assume the Season 1 Kirk wrap was designed to differentiate between the two Kirks in Enemy Within. Costume designer Bill Theiss kept experimenting with the look of the wrap (eg : Charlie's wrap in Charlie X; the version seen in Doomsday Machine). The wrap was resurrected in Season 2 at Gene Roddenberry's urging as a way to make Shatner stand out a bit more. Around this time GR was trying to deal with a lead actor who was getting less critical and fan attention than his co-star Leonard Nimoy. GR thought a special uniform might help calm Shatner down a bit. It has been speculated that the design also had two practical purposes : 1) it could be removed without messing up Shatner's hair, and 2) it sucks the gut in. Unfortunately, as anyone who has tried on one of these things will tell you, they are unforgiving on any extra poundage around the tummy, and when Shatner quit smoking in Season 2, he gained too much weight to wear the wrap, and it disappeared for good. I'm not sure about the TNG Captain's uniform - all I know is I loved it, and wish Picard wore it more often.
Charlie X has one of my favorite Trek bloopers, when Kirk enters the turbolift in his standard uniform and exits onto the bridge in the wraparound.
Special Captain's outfits continued on into the movies - Scotty had his suede "bomber's jacket" in Treks III & IV as "Captain of Engineering", and Kirk had his in Trek V. Seems to be a pretty common thing, actually. And Admirals all throughout all the 24th century series seemed to have their customized uniforms that were always differing from standard crew outfits. Hell, Admiral Satie in "The Drumhead" breezed through the whole episode in an evening gown.
Regrettably there are several instances in middle Season 2 where it's obvious that Shatner can't carry the wrap-around uniform anymore: some of them got 'disguised' by means of an undershirt of some description, but a notable exception to this was the fight scene with the Andorian in the corridor in "Journey To Babel", where we're clearly not seeing a stunt double for Shatner (for a change) and alas Bill's got a bit of an unfortunate "muffin top" going on when he performs those jump kicks.