Consider the distribution of Uber/Lyft drivers you have had. All the way from smooth driving, well-maintained car, through to erratic behavior and unpleasant environment. Imagine if the next time you got a driver you really like, you said "this driver only from now on" and that was the consistent experience you always got out of Uber/Lyft.
That is what Waymo is like. It is the same every time I get in. I do not have to think or adapt to a new environment. It is like sitting on my own couch at home.