Can you remind me of which airlines used the bubble for crew-rest? IIRC the original operaters all began with a lounge up there, including the piano!
None, and that's my point. Boeing designed it as the crew rest area, but the bean counters got there first and flight crews acquiesced. No doubt some $ were involved and the slippery slope became more slippery and steeper.
B747 replaced B707 & VC10. It had a longer range and thus it was deemed, by the designer, humanely appropriate to have an en-route crew rest area. Very progressive.
Reflect back on how the FE was 'bought' out of the flight deck.
Regarding accommodation in cargo holds; is it not the case that 'crew rest pods' for cabin crew on some carriers are in the rear hold, or at least under the cabin floor?