DESIGN SINGULARITY

What makes the difference between a vivid virtual world and a mere agglomeration of polygons? Is enough to reproduce every detail and hope that the life springs out magically? In other words, what else do you need other than the sum of the all parts?
It does not to be efficient!

I’m going to help me with examples from the Star Trek universe.
The TNG series used to build a story around every element, from the ignition button of Data to the flute of Captain Picard. This made the experience pretty fake for me.

In the real world, a stone is only a stone. We don’t bother about the story of that particular stone, except if it’s set in circle at Stonehenge, and it's right this that make them so relevant: there’s no other equal stone structures*.
Uniqueness is such thanks for an amount of other non-unique stuff. In the same vibe, we can define what is alive by defining what is not (do you remember Eraclito of Efeso?).

The DS9 series of ST is different: it’s a live world full of insignificant details, maybe thanks to the fact that is not filmed in the same four stages of the Enterprise starship.

Being efficient is part of the development philosophy, because making a game is very expensive, but the urge to fill more content in the same space is counter-productive, if you’re going to build a seamless world.

In Oblivion (or Fallout, GTA, etc.) you have a primary quest and a bunch of minor ones. Why could we not have only one massive quest?
Well, not only it’s not time-wise player’s friendly, but it’ll end seeming like a castle built in air.

That mass of secondary quests appears as the background for your main adventure, it let you remember that there’s something alive outside the boundaries of the “dungeon where you’re battling”.
For the same reason, I usually don’t play a lot of side quests, because if I finish them all, the world instantly lost its realness.

Mass Effect turns mainly around its big quest, substituting side stories with secondary activities. You can land with your MAKO tank on a planet surface and gather resources, and that's all.
It take no time to understand that those sections are pretty disjointed and, in the end, fake. What happens there does not affect your main voyage in any manner. Fortunately, the main quest is good enough, so you don’t bother much about the lifeless void left outside.

Far from being the only reason, inefficiency seems paramount for a real virtual world… or have you named all the stones in your courtyard?

*it's the same for other megalithic sites in Armenia, Scotland, Germany, etc.