To keep the city safe is a fundamental task of city’s streets and its sidewalks. (p30)
The obvious fundamental tasks of something are not always the only or sole primary purposes of such things, intended or not.
As with city planning, instructional design may sometimes be at odds with the symbiosis of fundamental and secondary tasks. There is always a balance between the local and the wider scale. With Jacobs, it is sidewalks as infrastructure vs sidewalks to create safety. In education there is content vs habits.