In TOS, the 289 M Enterprise was deemed large enough to be called a 'City in space' - enough space for 400 crew members to live on board in a civilised environment.
Unfortunately TNG era came through and subsequently everything set before that was down graded (from switch gear to carpet and to captains quarter sizes)
What made me laugh was in ST6 TUC, where you had the Excelsior, the largest ship in Starfleet and the captain's quarters was smaller than a junior officer's wash room from the TNG era.
I just rewatched TUC and got a giggle from that scene. I explained it away as perhaps he was sleeping in a smaller set of quarters/ready room near the bridge for quick access. I remembered touring the USS Lexington and that the captain had a small room off the bridge in addition to his larger quarters.