Simple preci: the medieval period gave us walkable cities. The twentieth century gave us drivable cities. Architects and planners holidaying in places like San Gimignano, in the 70s and 80s, saw an antidote to the whole world becoming like Houston, and tried to replicate those kinds of places in the boring cities they lived in. However, they had to water them down, eliminate the potential for tripping, give separation to houses facing the alleys, etc.. The result was too banal to be much fun for walking. What they ended up building, is better for cycling. And that is how cyclists inherited the post-industrial city.