My best guess is it's a busy road so it's dangerous and not really meant for bicycle and walking. I've done 13 miles yesterday to get a comic book on a bike and this right here is the distance between my house and a friend's house I told I can come on bike because what I just did gave me a feeling I could do it but my ass hurts so not right now. But yeah I want to see how this would play out. Before I would walk but I took a bike to a comic book store because it would've closed if I walk and I ended up getting there in time. Took longer than expected something that should've been an hour probably took 2 or 3 hours. So yeah I can do half of that for sure.
I heard that part of the motivation behind games like Pokémon Go is that they can collect data on previously unrecorded pedestrian routes between major landmarks or points of interest.
So Google’s directions may be based on crowd sourced routes that have never been vetted as safe/legal for pedestrians and cyclists.