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human
[Lord of the Rings] Why exactly were the black riders so dang meek?

Currently reading the Fellowship for the ~5th+ time.

The wise say at various points that the black riders were hesitant to commit to any action before all nine were assembled. But why? Why did they need to be so careful and meek?

According to Gandalf's speech at the Council of Elrond, Sauron had already "declared himself" openly some time after returning to Mordor from Mirkwood. And he was already warring openly on Gondor. Why couldn't the ringwraiths just go mess stuff up in the Shire and then Bree? Sure, Aragorn was at Bree, but what did the riders have to lose? And why were they so meek beforehand?

I realize they literally didn't know where the Shire was, but they seemed to get decent enough information when they talked to some folks. Even the Gaffer told them where Frodo was heading. And surely they could've easily tortured the hobbits for more information?

Between Bree and Weathertop, sure, Aragorn's skillful leadership would've led the pursuit astray. But after Weathertop, they took 17 days to get to the fords, moving slower and slower towards the end, and there was no sign at all of the ringwraiths. I know Glorfindel was hanging around as well, but the nine were clearly split up, so surely Glorfindel couldn't keep them all away at once, especially as he didn't actually know where the party was anyways.

Aragorn mentions at one point that, since Frodo was stabbed, they would be content to wait and let him come under the spell, their work nearly complete. So why not just finish it?

And they were there, ready, at the fords, and yet still somehow they don't block it off in time?

Or, to summarize it: Why take so many chances when we're talking about the freaking *ring*? Just get the damn thing.
gpt
I dont know if there's a canon answer, so just spitballing here.

- The Nazgul are ageless, but not immortal.  They can be killed by a good old fashioned stabbing with a magical sword, as the Witch-King finds out.  This makes them cautious to a fault, more interested in preserving their own lives than accomplishing any given mission for Sauron.  Even the most important mission for Sauron.

- Sauron had declared himself, but had not declared that he knew where the ring was yet.  We take it for granted now that everyone knows Frodo held the One Ring, but even Gandalf needed to consult some old scrolls to be sure, and took his sweet time doing so.  They didnt necessarily know that Frodo knew and understood what he had, but they know once they're assembled they'll tip off everyone to the fact that they're after the ring.  Once Sauron's enemies know they have the ring, there is the risk that they might use the ring, and might even master it.

- For a combination of the two points, the Nazgul might not actually care who their master is, so long as they keep their lives.  If Gandalf masters the ring and overthrows Sauron, he'll need lieutenants to spread his glorious perfect order, and the Nazgul will gladly bow to him.  From this perspective time is on their side; they're going to live forever, it doesnt matter who ultimately wins, so nothing, not even the ring, is worth risking their lives.  The idea that someone might actually destroy the ring is simply unthinkable.