As an aside, I was surprised to see how much of the aft space beneath the flight deck was taken up by the captain in Hermes. Below we see Captain's sleeping cabin, bathroom, day cabin and dining room. That's a lot of luxury on a carrier the size of a wartime CVE, but I suppose deemed necessary for a foreign station. I imagine this was a good place during the interwar China station tours. If I'm redesigning the 1925 rebuild of the Courageous trio the captain will be getting less space, with the focus being on whatever the ships need to maximize CAG size and overall capability.
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Ever heard the expression "the loneliness of command"?
Hermes wasn't designed for operation on a foreign station. That represents a fairly standard functional allocation of space on a warship of the period. Even something like a destroyer allocated spaces for the same functions. I also don't think that the space is quite as large as you suppose. These compartments were on the main deck. They are where the row of portholes are on the ships stern in this photo. Note how much flare there is on the hull around that area. That impacts the floor area available.
You need to remember that the captain was not, and is not, just one of the other officers. He only entered the wardroom by invitation. He ate, slept and worked (other than when required on the bridge or in other parts of the ship) in those spaces, separate from the other officers. He had his own steward to attend to his needs. Entertaining guests, whether at home or overseas was and is only a small part of his job. Move forward and you see similar allocations of space in warships right up until today with the QE class.
Just looking at the plans of the Illustrious class there are compartments allocated for the same purposes. Lower gallery deck aft, just inboard of the Port 4.5" battery, held Captain's WC, bathroom, day cabin, sleeping cabin, and deck below you find his office. In that case there were also a matching set of spaces for any admiral that might be aboard. I suspect the Courageous class would also have contained space for an admiral.
If you examine ships plans in detail, particularly carriers, you will find all sorts of cabin space allocated for various administrative functions that were absolutely necessary for the smooth running of the ship and its air group. Do you want to remove these as well?
The USN were and are no different. An Essex had a captain's pantry, state room cabin, bathroom on the gallery deck just forward of the island all duplicated for carrying an admiral.
Even looking at the plans for the Casablanca class CVE you will find spaces on the gallery deck occupying the space between 3 of the supporting beams for Captain's pantry, cabin, stores, bath and stateroom and running nearly one third of the way across under the flight deck.
A ship is not just a working vessel. It is home to her crew. But with rank comes increased responsibility and some privileges. I doubt many would grudge the captain a few luxuries.