But these are mostly just fast turnarounds, no? So you have very little time to actually see the location.

I'm not sure how things work in the US, but in the EU, most countries run diplomatic couriers on fixed schedules, often sharing the same guys, and they don't necessarily even get out of the airport. So, for example, every Wednesday the same courier flew down on the same flight to TLV, was met at the tarmac by the local embassy reps to hand over the "pouches" (which can actually take many forms), and then flew straight back. Not too exciting...