I would imagine that the Dominion War was widespread enough that not every ship involved in it stopped at DS9 at some point. How often did ships serving in the Pacific during WWII also serve in the North Atlantic?
Picard says that the Federation is over 8,000 light years across. Now, that doesn't mean it's a sphere 8,000 ly in diameter but that's still a vast area. It's more than 10% of the distance that Voyager had to travel to get home.
Space is BIG!