Why did they wait?

[McAvoy]

Well to be honest the NX-01 is a bad example. The ship's saucer is almost the same size as the TOS Enteprise with a crew of only 80. Granted you could say much more of the interior of the ship is taken up by more bulky and primitive versions of what the E-nil had. But primitive usually means that it needs more people looking after it than a more refined version.

...Or it could be the other way around...

Graham, the Defiant's level of living arrangements are similar to a Ocean Liner. Not first class of course which you could say would be the officer's quarters. But for the common crewmember, it would be far better than anything I was sleeping in while in the Navy. I had a 54 ft^3 living area. Enough to sleep in.

The HMS Queen Mary, not much larger than a modern aircraft carrier was able to carry 16,082 passengers in WW2. Graham, I doubt the ship's warp engines take up any more space than a modern vessel. Obviously the nacelles take up length and space, and a ship is much more compact than a Star Trek ship, but I doubt anyone can really think an Intrepid class is that much smaller than an aircraft carrier that if configured correctly (example, all rooms and corridors have bunks with enough room for walking space) that they should carry at least the same amount as a carrier if not more.

I do tend think there is a limitation somewhere. I am leaning towards a physical limitation than a energy one.

[SomosFuga]

Big saucer yes, but no engineering hull.

There has to be a limitation, but if not energy, nor space or live support, then what?

[Reliant121]

I imagine the limitation isn't one of technical design but of social expectation. The earlier TNG era Federation had always portrayed life in it as a utopian paradise which starfleet guarded; why should the guardians of utopia not have nice quarters? It seemed perfectly natural and normal to them to have enormous living spaces and so it seems to be a higher expectation of the quality of life.

It's not practical, but when has the Federation ever been practical?

[Graham Kennedy]

One thing I'd say in their favour is that living conditions have tended to get better over time on ships. Modern ships may be cramped, but for instance I've been on HMS Victory and the crew level there is 850 on a 3,500 ton, 227 foot long ship. A deck is mostly one big room with guns along the side where the crew works, and to sleep they just sling a hammock in their work space. Incredibly crowded, and food and sanitary conditions best left undiscussed. Conditions got a lot better by the 20th century, obviously, and continue to - the new Type 45 for instance are described as "luxurious" compared to previous ships, with junior rates in six berth cabins and almost all officers in single cabins - including all facilities being unisex. You couldn't get away with asking sailors to live in the sort of conditions that Victory had today.

And the ships are at least theoretically meant to be able to operate unsupported for years on end, something present day ships aren't (though in practice they never seem to do that in Trek).

[Deepcrush]

It's not practical, but when has the Federation ever been practical?

Kirk & crew.

[McAvoy]

One thing I'd say in their favour is that living conditions have tended to get better over time on ships. Modern ships may be cramped, but for instance I've been on HMS Victory and the crew level there is 850 on a 3,500 ton, 227 foot long ship. A deck is mostly one big room with guns along the side where the crew works, and to sleep they just sling a hammock in their work space. Incredibly crowded, and food and sanitary conditions best left undiscussed. Conditions got a lot better by the 20th century, obviously, and continue to - the new Type 45 for instance are described as "luxurious" compared to previous ships, with junior rates in six berth cabins and almost all officers in single cabins - including all facilities being unisex. You couldn't get away with asking sailors to live in the sort of conditions that Victory had today.

And the ships are at least theoretically meant to be able to operate unsupported for years on end, something present day ships aren't (though in practice they never seem to do that in Trek).

During the reactivation of the Iowas in 1980's they had to redo alot of the berthing because of sleeping conditions because the differences in 1940's vs. 1980's. Even the 1980's are different than today. Especially with the average sailor today owns a laptop and other electronic devices.

It also depends on various Navies as well.

US ships traditionally had more space and 'luxury' than British sailors. German sailors had the bare bones, the Japanese had something in between the British and the Germans.

It also can be said that larger ships despite larger crews will have more space than a smaller ship. Example: carrer vs. a destroyer or cruiser.

Obviously we are not talking about permanantly turning a Galaxy class or an Intrepid into a troop transport. Obviously there really hasn't been alot of evidence that Starfleet operates some form of equivilant of the Marines or a simple soldier. But I'd imagine there would be huge difference between an officer who will be onboard that ship for years and call it home vs. someone who will only be on that ship for only a few weeks or months.

Not only that there is a huge difference between a the crew density of a Constitution class vs. a Galaxy class. Using Starship Volumetrics, takeing away the nacelles, the Galaxy class has 30 times the volume than Kirk's TOS Enterprise. At a crew of 430, the E-D should have 12,900 crew. But in reality, she carries only a 1/12th that which included civlians like kids and spouses.