With the introduction of the runtime NavMesh API in 5.6, we got one step closer to awesome procedural levels and user-created levels out of the box. But some larger levels and/or levels with a lot of details can get really slow at times. This is where occlusion culling can help.
The occlusion culling in the editor can do wonders at times and the ability to use it at runtime would really benefit games that created semi-large levels at runtime or user-created levels.
And you can think; it takes a lot of time to bake. And of course it will take time but if you want this in your game, you can probably find a way to integrate it so it seems seamless.
Personally, I would use it when exporting a level from my level editor.
When baking at runtime, the developers should get access to some serializable values. I don't know exactly how they are saved in the editor but if Unity can do it, so should we be able to. So you can save it to a file and then load the occlusion data at runtime.
This would make the procedural and user-created levels area pretty much complete when it comes to providing easy to use and powerful tools at runtime to contribute to the game.