Could be due to crew numbers? I mean compare pikes Enterprise to TOS era, and double the crew gets you a lot less quarter space (pike's quarters in particular clearly get subdivided to hell by TOS). Maybe they were too cramped with increasing crew numbers.

Looking through MA it mentions they were meant to have an operational lifespan of 18-odd years, given their battle positions and exploration use (both high attrition) it mught be that they were seen as the sweet spot between endurance and disposable