I have not personally been able to verify this since the last time I was in the bubble (in 3.0) but then - at the Tourism economies only - there were definitely one-way passenger missions (both bulk and VIP).
Round-trip missions to see the tourist beacons can be obtained from anywhere, of course.
There definitely ARE one way missions. I have flown 2.
Tourist missions are return, as are famous explorer missions. But politicians, businessmen etc need to go one way sometimes. Remember that both tourist and famous explorer missions have a beacon as a destination. There is no where for a one way trip to drop them off. Whereas the other sortsof missions have a station or planetary base as a destination.
These one way missions are indeed rarer. Most colonia missions seem to run out of tourist economy systems, so naturally those passengers tend to be tourists. I have yet to find a system that reliably has one way missions, or figure out what conditions you need to have for those missions to be generated.