One Or Many Worlds?

Fantasy writers know modern cosmology but continue to write stories in which extra-cosmic forces seem to focus specifically on just one planet:

when Neil Gaiman's Dream of the Endless enters the waking world, it is the waking world of Earth;

in the seventeenth century, Destruction of the Endless abandoned his realm because Newtonian speculation about the inter-convertibility of light and matter was the first step towards nuclear conflict, as he knew from his experiences in many other worlds - this implies that the Endless base themselves in one world at a time;

when Mike Carey's Lucifer creates a universe, he and others from his father's universe visit only a single planet in the new universe;

when Lucifer's protege, Elaine, creates a universe, she focuses only on a single planet within it and finds even that difficult.

However:

Death of the Endless says that she is simultaneously present for the deaths of organisms on an extra-solar planet;

the single Martian living on Earth sees the Martian Dream;

Gaiman's current The Sandman prequel at last shows Dream's interstellar journey which involves extraterrestrial aspects of Dream.