As can be expected during 11 ½ seasons and a movie of constant use, there were numerous exceptions and oddities over the years that this uniform was used.
Firstly, Chief O'Brien wore his uniform differently; he constantly wore his sleeves rolled up - presumably for a more "hands on mechanic" kind of look, since he was an engineer and the Chief of Operations. It was a nice way to visually set him apart from the rest of the Starfleet crew in that regard.
For some reason The Powers That Be decided to go for a similar look on Riker in Generations (except with only his jumpsuit's sleeves rolled up, not his undershirt's):
Maybe they had Riker roll up his jumpsuit's sleeves just because they were too short, there was no time or money to replace them and/or make him a new set of uniforms, and it was simply decided that inexplicably rolled up sleeves worked better than sleeves that were obviously too short.
|"Might as well make it part of the plan and then it'll feel on purpose."|
The following production year, for some bizarre reason, the EMH wore both his jumpsuit sleeves and his undershirt sleeves pushed up (a la O'Brien, except his undershirt sleeves were rolled up rather than pushed up):
|VOY, 2x21 "Deadlock"|
This really makes very little actual sense, as a holographic being (especially one who could control his solidity at will) would be quite unencumbered by its/his holographic clothing while working, nor would such a being be overheated or uncomfortable in long sleeves unless programmed to be so.
Maybe he was experimenting with his physical wellness (such as making himself sick in "Tattoo), experimenting with his appearance (like how he had hair in the alternate future of "Before and After"), or some other such thing.
'course, he only ever did it in this one episode, and it's not a bad look for him, so maybe it's best not to think about it too hard.