The interesting part here is... the Waymo has no reason to. There is no driver. All cameras and sensors are outside. It's just for not freaking out the passenger :)
https://www.reddit.com/r/oddlysatisfying/comments/6biyr8/way...
We have very different thresholds for what's interesting.
The platform provides this feature out of the box, why would waymo go out of their way to disable it. Obviously potential occupants would appreciate seeing out the windshield if it's raining, why that is interesting escapes me.