I don’t always run a timer, but it is a tool in my box.
Mostly it comes out when I feel like the players are spinning their wheels. Like, they know they need to get into the server room on the 10th floor. There’s a front door with security, a back door with an alarm, etc. The players are just going round and round with ideas but not doing anything.
I’ll say “I’m starting a five minute timer. If it hits zero, something interesting will happen”.
If it hits zero and they’re still stuck, then as foretold something interesting happens. A rival group rolls up and firebombs the entrance before heading inside. A security drone spots them and is calling the cops. Whatever. Something that forces them to act.
In combat rounds I sometimes do the same, but only if it feels like they’re not making progress. Maybe it’s a little rude sometimes, but I value keeping the scene moving forward. I don’t want to keep spending three minutes on “should I move? How far can I move again? Is there a range penalty? What if I use a spell first can I still shoot?” stuff. Especially if it’s rules minutia they should already know.
The amount of times I had to remind an old group’s bard that yes, in DND 5e you can move AND take an action was too high.
I think people have radically different ideas about what “minimal background information” is.
Some people think the Silmarillion is a suitable primer for their setting.
Some people have like one paragraph for the big picture, and one paragraph for each major faction.
There are players that would say both is too much.
I think a couple short paragraphs should be enough for a quick start for a custom setting, but I’ve had players that just refuse to read anything at all. As someone else said, it’s makes it really hard to do some sort of stories if all the players are utter neophytes/amnesiacs/from-another-world/etc
I tried to do a game of Vampire once, but the players refused to read anything about the setting. All the political intrigue fell completely flat because they didn’t understand what the different factions were looking for, nor did they understand how vampires worked.
That group might have just been kind of bad players, but I feel like bad players are more common than good. By “bad” I mean “doesn’t think about the game very much, doesn’t retain anything about the story or rules”. They couldn’t really do anything more complex than a simple dungeon crawl.