Actually Byron there are many reasons some boats have wall paper. (actually usually vinyl). One reason is that very frequently "inferior" decorators were hired to jazz up the look so they sell at boat shows. Folks in the marketing department are trying to make it look like a movable condo. In some cases, it really looks fine (depending on individual tastes). Our vintage Hatteras' were built mostly with wood interiors such as teak, afromosia, mahogany and that so called modern white ash of the late 80's and early 90's. A little wall covering tastefully done such as in the heads IMO looks great and has a practical purpose since it is relatively easy to keep clean. My 1982 Series 1 48' MY was made with mostly wood interior but did in fact have some vinyl wall covering on the bulkheads leading down to the aft passageway. A look at the brochures section of this forum will give you many pictures of older Hatteras interiors.
Now to address your question as to why someone would cover beautiful wood on a Hatteras.... Sometimes it is a misguided attempt to make it look more modern or different but quite often it is as you suspect, to hide blemishes such as water stains. My present 48 MY interior was wallpapered, painted with Imron (off white) or mirrored when I bought it. It looked to me like it belonged in a house of ill repute in New Orleans but I figured that as a woodworker I could remodel the entire interior, which I did. It came out well but it was a much bigger job than I originally thought. The "while i'm in there's got a hold of me and made the job much more involved and I ended tearing out everything including the paneling, trim and most of the original cabinets. It was mostly a labor of love and mostly fun but I wouldn't do it again even if I was younger. Another HOFer (Bobk) has a sistership of my 48 and his interior looks like it recently left the factory. Matter of fact the entire boat is unusually well maintained. He did pay a good bit more than I did but if I had to do it all over I would have bought the nicest one I could find and just take good care of it.
BTW, most original interiors can be restored if you want to work hard. Yachtsman Willy of this forum took on a sinker (large boat, I believe around 60+ ft) and brought the stained original wood interior back to a fine looking interior, but he worked very hard and long on it. Another forum member (Q) is completely rebuilding a Roamer Yacht and is doing such a good job that it seems like a shame to put it in the water.
Walt