It's useful, but a lot of places have a central dispatch that covers an entire county, or in some rural areas even a couple different counties. The center I work for covers almost 500 square miles and about 70 different towns, I've lived in this county my whole life, I know about half of the towns pretty well, the others not so much, and there's maybe about 2 or 3 that I'm genuinely not sure if I've ever even driven through them, let alone spent any time there, so any familiarity I have with them is only from my job.

My personal familiarity with some areas does come in handy from time to time, but it's not absolutely necessary in most cases, you pretty quickly learn what questions to ask and how to use the tools that are at your disposal to work around the gaps in your personal knowledge.