What is stopping IPACS from adding multiplayer?
They are getting a great income from the yearly flight sims and in game purchases (If each sim was 5 usd, and got 10k downloads, they would get 50k usd yearly, not counting the in game transactions and their PC version, although I do agree taxes and employee salary exists)
They can add a subscription as well for multiplayer (I would prefer a non renewing time restricted purchase like spotify tbh)
The only reason that would make sense would be the lack of technical knowledge of multiplayer servers by IPACS.
Still,I wonder how, many mobile games manage multiplayer rooms for Free while offering only tiny one time micro transactions (Not even necessary to purchase for multiplayer)