In the Netherlands, the average biking speed in Amsterdam is 14.9 km/h. "In the popular cycling regions Drenthe and Overijssel the average speed is highest: 15.8 km/h." - http://www.holland-cycling.com/blog/260-amsterdam-has-slowes... [1]
9 mph = 14.5 kph, so nearly 1/2 of the cyclists in Amsterdam cycle "awfully slow" by your scale. The point is, they do bike. Though the average trip length was a bit over 5km, not 24m.
[1] This was by 55,000 cyclists who voluntarily participated in National Bike Counting Week, so may not reflect the general population.
And if we're talking average American commutes, a lot of them involve routes where you might have only freeways between you and your destination.
It does not obviate the need to visit a gym.
He probably would also disagree about what's most straightforward. I recall him recommending running in the book because it doesn't require any special equipment or training, in contrast to cycling, weight lifting, swimming, calisthenics, etc.
To be clear, I do think strength training is important as you age to avoid sarcopenia. But I suspect that running or cycling would provide enough resistance to slow sarcopenia for your lower body, making other exercise more important for your upper body and core.
https://www.webmd.com/fitness-exercise/features/no-gym-requi...