Well, you've lost me here. What is the GM presenting - beginnings? or endings? Beginnings don't need much of a world, as per the example in my previous post: tell the players to look at the PHB and build something out of that. As for endings, they don't come from the GM deciding in advance. They come from playing the game. And the necessary setting for framing and resolving a situation can also be provided by the GM in the course of playing the game.
The GM is the narrator. I like to think of him as the criminologist in Rocky Horror.
The players are both the audience and Brad, Janet, Columbia, Eddie, and Rocky.
When the criminologist speaks he is both telling part of the story, but setting up the next challenge in it. While telling it he knows where the story is heading, but even to tell the story he had to piece it together from what the players did.
So he plays both parts of the movie, but one of the is off-screen. When he narrates what he found he is offering the situations just as they were offered to the players, and we see the "action" that happened because of the results of the players choices.
So the DM knows where the story is headed, and what is to come in the story. Just the players often contort that skipping parts, and making others loop back on themselves.
Yeah you are offered NAMES for things, and if you don't like the very few selections, you have to work from the ground up. The planes can be thrown out. Leave Planeswalking for Magic The Gathering as I never really cared for it. As others mentioned there is a lot of little stuff, but no setting. You must create the world, as I said before, because you are sitting in the Ivory Tower with this little bits of stuff floating nearby otherwise surrounded by The Nothing. Because nothing is what the PoL setting is for a
setting.
What empires are in the PHB or DMG?
Huh? Permeable means permeable.

Therefore it is NOT cut-off or disconnected in in way, but secluded.
Darby O'Gill likewise was not supposed to return after following the king and IIRC he did not...until the king played a final trick on him for his selflessness.
But it wasn't cut-off, just secluded, as there WAS a natural means of getting there.
Their terminology and word us is lacking, in many areas of 4th edition.
I wasn't in any doubt that you don't like the default 4e setting. But it doesn't follow from your dislike
Previous editions had a medieval backdrop. You plugged the game into it. 4th has nothing. If you assume still a medieval backdrop then it wasn't because this was offered. It also looks a bit silly to MANY as you are no longer in a human-centric world.
These are two pretty big elements of a setting. In past ediitons it was explained why elves didn't rule the world through the mechanics of them having level limits. This was lifted in 3rd but their lifespans still remain very long. I am not sure 3rd took care of the problem and didn't end up having a elf-centric world.
4th I am not currently sure which race would rule, but the concept MIGHT be fixed if for some reason one assumes that ONLY the PCs have levels. But that dissolves my suspension of disbelief when one human can be a PC, but another cannot as there is absolutely nothing that prevents them outside of the game mechanics. If the setting said, some were born touched by gods or something, but the gods don't even participate in 4th and are there by name only. See the discussion about "paladins are always paladins and never fall" going on around here somewhere. PoL offers a few things, but in doing so sets up mixed signals because it doesn't really know what it is.
If you are giving me a setting, then give it to me. If you are telling me to make it, then get the hell out of my way and don't open your mouth with your ideas, so I CAN make it.
LotR does this nicely by starting off telling you about Middle Earth in that the world of [hu]man is coming.
W&M (which you yourself deny establish a setting).
Never read the book as I wouldn't pay for advertising. If it was an important part of a setting, then it should be contained in one place, and being the default setting, should be in that place in its entirety when the game comes out. Not requiring the thread on trying to find the bits and pieces of it that have been presented over 2 years in all sorts of places.
What did your play actually do to "build" your settings? Note I despise the use of the word build for anything that is not a tangible structure.
Did you have a town spring up because the players suddenly wanted to visit it with JIT DMing? Did a race suddenly come into existence?
What significant thing about the setting did this JIT create?
I don't know what your approach to GMing is. But I know that I can run a session for my players with nothing but a map, some inhabitants and a few ideas linking that situation to the myth and history of the gameworld.
I don't even need that much before I sit down to run, but that isn't my point. You and I are not the only players.
The popularity is based on the number of players. If 4th isnt popular, what could be the reasons. That is what we are going about in this thread. I think?
Well I agree that a lack of setting for those, unlike ourselves, could be a big reason. Again taking into account all other forms of entertainment made to envelop the reader in it, 4th is very lacking in getting things across that could envelop many.
Maybe the setting is there, it is just hidden in the tactical grid based game.
The problem with your quantum mechanical analogy is that a fiction doesn't have to have a state until the author chooses.
The problem you seem to be having is WHO the author is. The DM is the set[ting] designer, director, and editor, and the players are the screenwriters.
Thus the DM must make the story fit in the set designed. It doesn't mean a new set can be made for a change in ACT VI once the play is in action.
Once the play is in action for OTHERS to view, all things should have been figured out.
Imagine viewing the story AFTER as that is how others would. The screenwriters may want something, but the director has already decided what will work in the world.
James Cameron said:
Luckily he played every part, but as the director, had they not had "bewbs" the director chooses and can override the screenwriters choice.
Likewise the same for dragonborn.
The players, screenwriters, only use the tools given put a story together with them, with approval of the director.
If I'm making something up, I don't check it.
What are you creating that is so significant to the setting? Flammable jewelry is really a novelty bit and doesn't nor should it, play a large role in the overall plot unless that is what you wanted.
I work in either of two ways. I have things done in advance or have NOTHING done in advance. The problem with having nothing is as I explained before, you MUST have something still: the setting. I do always have something. cities don't pop up over night while the characters sleep.
You have to have a foundation before you can build a house. Your maps, and such ARE your setting. JIT doesn't create new maps for you "on the fly", you must have them in advance of playing in them.
If you leave an undescribed location via "HERE THERE BE DRAGONS" on the map, then you already decided to place something there later when needed. You didn't make the world bigger, you just colored in the drawing already there. If nobody ever visits that area, then your setting was still created from the start as there is still nothing there now. The void has not been replaced and its state remains unchanged.