As @woa.17.wewak already said, they do exist.
Such as Aeroflot, S7, Rossiya, IrAero, Aurora, Ikar, UTair, Smartavia, Nordstar, Pobeda, Red Wings Airlines, Ural Airlines, Yakutia Airlines, Nordwind Airlines, Volga-Dnepr Airline, Royal Flight, Yamal Airlines, and others.
They haven’t been added to the game yet.
Hopefully, they will appear over time — that would be great.
Not entirely true — there are international flights, but not many, mostly to Asia and neighboring countries.)
This is an example.
I understand, it makes sense given the current situation.
You’re right, that’s how it is at the moment. But after all, this is just a suggestion and a discussion, like most other airport proposals — some of them may or may not have a chance to be added to the game.