[nhaehnle]

If a cab driver refuses you service take the next one.

While the population in large cities is growing, plenty of people don't live in one. "Take the next one" simply isn't an option for those people (I speak from experience, having lived in the countryside).

[tsotha]

In this day of Uber and mobile phones it's hard to believe you can't get a cab pretty much anywhere.

[nhaehnle]

How about a remote valley in the Andes?

(Somewhat tongue in cheek, but it's good to remember that there's more to life - and perhaps even potential markets.)