In many cases, as in machine journals and bearing surfaces, a high polish will cause problems. Oil doesn't carry on a really smooth bearing surface as well as one with a little 'tooth'. Piston bores are honed to give a criss-cross pattern to hold lube, and prevents the cylinder from scoring.
Does a really smooth finish on a barrel could cause pattern problems, like wad sticking or buildup of films? I don't think felt or paper wads would be any trouble, but plastic wads could start to heat and melt to the bore.