>>297585568
Unity 2018 combines the probes, maps, etc in a big lighting data file. It gets big.

>For large outdoor shit I figure there ought to be a way to generate one on runtime off of the sun light no?

Realtime lighting is shit for performance and looks bad. You want to bake as much as possible. Always better to download a bit more in vr because you want to do everything you can to hit that sweet 80/90/120fps. Same way vrchat adds a ton of network traffic because the IK is precomputed so you don't have that overhead of doing it for every person in the room.