That's not all that solid an argument, because Ready Rooms are a real-world phenomenon rather than a TNG-invented one. Skippers have bunked next to their command centers during alerts since time immemorial, in the Chart Room if nothing else was available, and in
the centers back when no separate bunking existed yet.
TOS was free to ignore Ready Rooms like it was free to ignore Sails or Gun Decks as shipboard fiction elements; TNG was free to include such things (with the appropriate futuristic twist, hopefully). Beyond this, it becomes a matter of continuity - but one that has to take into account the real past that supposedly precedes the fictional future of Trek. Thus, anything missing from TOS but present both here and now and
in TNG calls for an explanation of some sort...