One advantage of camo uniforms for working utility uniforms is they tend to be effective in hiding things like grime and mud, which consequently means you need to launder them less frequently to keep up the same appearance. If you've got a solid single-color uniform, chances are that these will stick out like a sore thumb. That was one thing that sailors liked about the old US Navy NWU (the one that camouflaged you very effectively if you fell in the water)--really good at hiding paint drips.

With regards to looking good, I don't think it's necessarily that the look good with appropriate materials, but more that they look good only when they are properly starched and the like to maintain crisp lines.