As for "sphere of influence and connections," well, aside from the above and another possibility I gave (bardic tales), many settings are magic-rich enough so that long-distance communication is a thing.
Sending stones are an uncommon item, and that's only if you go by exactly what's in the DMG--how about a more useful version used by organizations (such as a Merchant's Guild) to learn about important things (such as merchant vessels), who then provide some of that information to other interested parties?
And there can easily be
nonmagical reasons for long-distance communication--the D&D webcomic The Weekly Roll has a spinoff about
postmen (who apparently all have class levels, because the mail
must go through). There's the idea of carrier pigeons, which in D&D could actually be intelligent or magical beings (there was a form of tasked genie back in 2e whose entire purpose was delivering messages). There's even the possibility of a pony (or hippogriff!) express.
My own upcoming Victorian-ish setting, thanks to the fact
artificers exist, has telegrams and telephones, even if they're too expensive for most people to use regularly. The newspapers can afford them, though. If any of my players were playing a sailor, I'd certainly let them learn about ships on the other side of the world.
Sure, it's more that possible to have a setting where there's no way for the PCs to know anything about the world more than a few miles from their hometown: a low magic, low tech setting where few people ever travel. But are you really saying that people who
aren't playing in settings like that should be just as limited by the rules as those who are?