Someone appreciates the big bucks spent on that gun! Keeping them polished like that is harder than one would think, and they stand out from a distance when that polished.
I don't know why, but me personally I like a little tarnish on those guns.
EDIT: Is it me or does that gun look a little small?
Yeah, it is the case that some units limit how much they polish their original tubes because those are actual artifacts (meaning some of the surface marks were acquired during the actual war so not to wear them off with polish).
This gun appears to be a spankin' new reproduction, freshly painted carriage included. In which case go ahead and polish the dickens out of the tube if that's what"torques yer tube"! To do so challenges no functionality at all; there's no metallurgical reaction of any great consequence to a new gun.
Way to pretty for my taste. Its hard to see the front of the tube but it doesn't have a sleeve in it I doubt they fire it. @Gettmore did they fire this piece?
When I build my 6lb howitzer I work very hard to give them the been there done that look.
Looking at the piece, with its size compared to the Infantry in the background, and the muskets stacked this gun looks half-scale in size to me, but it could just be the picture playing tricks on my eyes.
A steel internal sleeve is insurance that the gun won't burst. It reinforces the barrel internally for its length, and can be rifled or not. Most, if not all, modern reproductions are sleeved for that reason. It's detectable on the muzzle face, one sign that the piece is likely a repro. You'll see a bi-metallic border there, easier to see on some tubes than others.
bs answer is that Artillerists are known to "wear their heart on their sleeve," which in the case of some battles gone bad was literally true.