We have especially played prologue one-shots in one campaign I am in, when a player couldn’t join. They added to the worldbuilding 
Or if an event happens somewhere else that will affect the group later

Mama Strange

Yes! I have done this a few times with my long-running planeswalking game. I have done:
a flashback for a new player joining the game showing the events that led up to them joining
a side story featuring a different party of adventurers the main party has heard about and encountered once or twice
one of the players took over as GM for a time, allowing the party to explore the dungeon within that player’s mind
players got to play a “videogame” within the world of the game, and played as characters within that game
All of these were fun and interesting, and seemed to go over well. I took care to make sure they fit within the narrative, feeling more like scenes from a film or tv show that added but weren’t too jarring.

Sir James

I think I’d be happy to see parts of the world unexplored, and get to play with different characters having different stories, but I also mostly run and play one-shots. That said, for a one-shot break from the regular campaign, my preference is to usually play a different system and/or setting. 

The Merlitron

I have run and played in-game one shots and they can be hit or miss; my personal best experiences are when the table wants to play still but is missing enough members that the normal game would usually be cancelled. In the Witchlight game I’m running, we had a game that was going to be short several of the table so instead of continuing the main plot, I let them explore and we had a tiny one-shot where they went to an underwater fey market, explored an old battlefield, and otherwise were just tourists for the session. They got some fun swag and lore drops, we got to play, and the rest of the group did not miss any important plot developments. 

Nyx

I’ve done this as a way to play my character in a different system entirely. It was a Pathfinder 1e game and we did a dream sequence in 5e, so similar to a dream, things didn’t work the way we expected. It was kind of a fun way to still play when some of our players had to miss the session. 

GamerMomLuna

I’ve done this. I had a few players that were going to be out for our normal game day. I planned a one shot that took place in the next dungeon the main PCs would be in (the players did not know this). The events and changes in the dungeon from the one shot influenced how the dungeon looked when the main campaign PCs arrived. 

Crazy Weazel Gaming