The Excelsior, as it was presented in Trek III, was supposed to come across as more of an automatic "appliance" vs. the moving sculpture of the Enterprise. That's how Scotty was able to sabotage it the way he did. It reflected the Federation stressing technology above people, similar to the sentiment in The Ultimate Computer in TOS. And I really think that trickled down to the 80s sharp-edged aesthetics of the ship's lines and the sterile look of the bridge. I just don't think it was originally conceived to be the workhorse class of the federation it eventually became, but it had to serve that purpose due to budgetary constraints with the FX.
Styles kicking back to a cup of coffee on the bridge was symbolic of the idea that you didn't have to be on your toes anymore to run a ship, as was that scene of him lying down in his quarters filing his fingers when the yellow-alert came in. Later on, Sulu kind of changed the meaning of drinking coffee on the bridge to kind of a sign of having finally "arrived" as a figure of veneration. Picard always limited hot drinks to his ready room.