I think a big part of not knowing regularly taken routes is just over-reliance on GPS and subsequent self-doubt. When I am in a foreign city, I check the map on how to walk somewhere. I can easily remember some sequence of left and right turns. But in reality I still look again at the map and my position, to "make sure" I am still on the right track. Sometimes I check so often, that I become annoyed by this phone looking myself and then I intentionally try to not look for a while. It is stressful to follow the OCD or whatever to check at every turn. If I don't have to check at every turn or maybe call it sync my understanding of where I am with the position on the map, then I have more awareness of the surroundings and might even be able to enjoy the surroundings more and might even feel free to choose another, more interesting looking path.

For this experience I am not sure, whether people really don't know regularly taken routes, or they just completely lack the confidence in their familiarity with it.