Live traffic is partly drawn from open sources like FlightAware, but that data is only as good as what’s provided. Between latencies in the feed and the lack of an end-to-end (i.e., at gates,T/O, enroute, arrival, at gates) status, there are phases that are derived or assumed rather than explicitly shown in-game. That’s not MS’ burden.
Tying live traffic to airport activity at the gates and ramps would bring your sim performance to it’s knees. As it is now, even just turning up airport activity sliders eats away at your FPS rate. Imagine what happens if the server needs to track that in real-time vs. a pre-calculated and non-randomized setting, and that’s happening even when you’re just flying near or over an airport/field. No thanks.