Oh, I disagree, this is something I observe and in fact do myself quite a lot. We all run it through our minds which route might be the quickest spending on certain factors. The difference is Waymo (or any tech) will base this on actual data (i.e., getting there quicker) vs humans who will be more emotionally driven (i.e., frustration at the driver in front, wanting to take the more scenic route, being undecided about stopping at that cafe halfway).
I'm all for self driving in highly populated areas. In a perfect world I'd like to see it integrated into all vehicles, and when entering specific areas you are told your car will enter self-driving mode. Arguably this makes the most business sense for Waymo, licence the underlying tech to manufacturers that already have capacity to produce vehicles vs compete.