Let me give two examples:
You are a customer in a bank office making a loan. The room might look like a regular office, but really this part of the office is very limited. This part of the office deals with visitation-like business. If one of the staff here has sudden diarrhea he won't just drop top secret documents for anyone to steal from his desk, because anything high-level wouldn't be done from the same room.
You are invited into a police office to leave a detailed report. It looks like an office but again only a division responsible for visitation-like business. You can't just sneak a peak at someone's monitor to see a spreadsheet of undercover police, because even if that cop has a high-security password, the risk of some unexpected contamination to the visitors is too high.
What I'm describing is not just a reception or visitation room (like prison), or storefront that's entirely meant for visitors. I mean kind of a working room/office where work is done, but with a lower level of security. The point being that if someone makes a mistake (like throwing his highly classified papers unguarded at his desk because he has to rush outside) then that mistake is greatly reduced in severity because his desk is in a completely different sector than the more public sectors.