Separation of domestic and international departing pax

[davidjohnson6]

In many airports of the world, departing pax whose journey originates in an airport go through a centralised security screening. Once passed, depending on the immigration policy of the country they are departing, they might also go through an exit immigration process, either at a gate, or as a filter towards a number of non-domestic gates. However, the same security screening area covers those departing to both domestic and international destinations

Occasionally, I've flown out of airports built in the last 10 or 20 years, where the route from landside is completely different whether one departs to domestic or international - i.e. entirely separate security screening area, departure lounge, etc
Having a single security screening area for locally originating departing pax probably saves money, and having a separate domestic departures lounge likely reduces the average retail spend per pax. Adding complexity of design in buildings is rarely done without good reason. I should stress I'm not talking about cases where there are 2 or more large and substantially separate terminals - I'm talking about airports of modest size whose terminal could have been designed to have a single departing passenger pathway in one building

There must be a good reason for airports built in the last 20 years to have been designed this way.... so what's the rationale behind this ?
Airports in Europe that follow this design that come to mind include:
Bulgaria - Sofia T2, but strangely not Burgas
Ukraine - Kyiv Zhuliany, Lviv, Odesa, Zaporozhye, Kharkiv
Additionally at these airports, departing and arriving pax are (I think) segregated... so the possibility of an easier pathway for connecting pax doesn't really apply

Apologies for starting another question thread, but there seem to be an awful lot of knowledgeable people on here who are generous with their time in answering questions and I hope I'm not abusing their goodwill.