Usage examples would include e.g. loading options and changing resolution appropriately and similar stuff.
You can’t access game context there, you need to delay whatever you’re doing until Update gets called.
The reason is that the object in question might be being constructed as part of a world starting up or some other scenario. It’s also possible the object is being constructed on a dedicated server, which has IServerContext instead of IGameContext.
If you need to set up resolution initially, the best place to do this is to override the methods in CoreGame that relate to resolution and window configuration.