I applied a year or two ago, and have received various invitations for onboarding - which always seem to happen at times like Saturdays 2am, or Tuesdays 8am (PST).
I don't know all potential routes in a 20 mile radius of my home, no.
In a large metropolitan area, there are literally many hundreds, if not thousands of miles of roads within such a circle.
And something changes every year. Sure, someone who does nothing but ride, day in, day out, like a bike equivalent of an old school taxi driver, would learn them all after some time. I don't have that amount of time to spend.
I don't see traffic jams formed by bikes, no, but I regularly see construction crews regularly closing bike lanes and bike paths for work, for parking their construction equipment, or for setting up temporary signage.
Not going to happen at those hours.