AmnesiaPlayer...
The very idea of making a level seem believable is (just like many other things in design) just another problem.
This problem is solved by layering details. It is not the best practice to give everything in the Game the same amount of details, simply because it could have an impact on the performance, or even higher the creation budget.
Just like you could read a car's licence plate from a meter, but would struggle if the car was on the other side of the parking lot, it is better to create a high performance low quality model. You could then argue that if you go close to it again, you would see that it's low quality and here's where skyboxes come into the mix.
There is a good design principle of not rendering what cannot be seen, if player can't get somewhere, use low quality. If player can't see somewhere, don't render it.
The usual game level (in an open space) would consist of something like these layers:
- Player Gun / Lantern / Hands
These are the things to get the most detail. Notice that in Amnesia you can even see Daniel's hair on his arm...
- Things very close to player
This depends on engine and graphical settings, but it the usual detailed stuff that is being rendered to it's full potential. Try changing Amnesia's graphical setting to the minimum and observe the increase of texture quality when you're really close to the ground and from the standing height.
- Things close to player
Usual detailed things that create gameplay but can be for example rendered in lower quality by the engine because player is further away.
- Things player sees, but can't get to
Here we get into the interesting part. This is your usual static trees, low res buildings but also MOVING CLOUDS (as actual objects) and also rain particle effects...
They are usually really far away and Player won't see them up-close.
- Enhancers
Here is your skybox. I intentionally made this my last point, because if we don't use skybox for now and use a solid color instead, the final look is actually pretty good. You have your buildings in the distance and even your clouds moving. (or explosions as objects). We add a skybox as a solid backdrop to all this to tie it back together with it's color palette and to provide something to hide the fact that behind that low red building is just a plane and then fall into the abyss.
Would you invest money and effort into making an animated skybox? A 360° video playing constantly in the background? Or would you rather create some low-quality large objects in front of the skybox but far from the player to hide the fact that the skybox doesn't move.
I don't deny that some skyboxes might actually change and move, that might be a thing. But you really really don't need it that much.
I hope it answered your question.
Also!
Some skyboxes don't animate... They just rotate and fade into another skyboxes.