Field uniforms are different than dress uniforms. This is a dress uniform and it is used to show off your accomplishments and affiliations. Field uniforms would be more like Major Hayes from Enterprise. His uniform is drab and you can't easily tell the difference between him and his subordinates.

This isn't the uniform they would wear for actual boots on the ground warfare. These people are the equivalent to the navy not the army or marines. Snipers arent picking Admirals off regularly on their own ships. If they went "ashore" it would make sense to have different uniforms unless they were knowingly doing a diplomatic mission on that particular plant at that time. Then you wear a dress uniform. There's a reason dress uniforms look different from ACUs.

Helps they're on a ship, never really on a battlefield

Because the chain of command needs to be embedded enough into your psyche to override your fight/flight response. Same reason we spend our entire careers in the military practicing war. When it's real, you can't freeze up or get flustered...your job also has to be so well practiced that you can do it instinctively, because when you're getting shot at, instinct is sometimes all you've got left.