Our own world is full of loose threads that will never have a resolution of which we personally become aware. Fictional literature in general leaves many things unsaid, unrevealed and unknown. I know of no writers who can neatly package their works to answer each and every question about "what happened next?"

"And they lived, happily" glosses over a number of details. It also ensures interest in revisiting an author's world.

There are always mysteries that we will never personally solve. They may be answered in passing by another, they may be totally ignored.

The need to have every last reference explained in detail is pretty recent, I think. It's ok for the world to still hold secrets.