Models are typically smaller scale/scope... So a "real urban center" could probably easily provide service that smaller cities can't.

As to why Iowa City doesn't run on Sundays and Federal Holidays:

The University is about half the population of the city. The University runs a separate "Cambus" system[1] (that the community can also use) and after-hours routes for students[2].

We're also still in relatively early days of finding out how Iowa City residents use public transit when there's no barrier. For instance, they stopped running the downtown shuttle and reduced the number of stops downtown[3] because downtown is relatively dense, walkable, and student-heavy (i.e. mostly young, healthy, ambulatory people) and served by the University.

There's also a growing interest in adding service to nearby towns and adding Sunday service, even if it's in a limited capacity.

1: https://transportation.uiowa.edu/cambus/cambus-service-calen... 2: https://safety.uiowa.edu/nite-ride 3: https://www.icgov.org/Home/Components/News/News/2165/390