[dragonwriter]

> So I would be surprised if there is any federal form that requires you to put the "city" you live in, outside the context of a USPS address.

Forms that ask for separate physical and mailing addresses often use the shape of a USPS address for the physical address (including ZIP code), even though many of the fields may not apply. “Physical locations all have addresses shaped like postal addresses” is a common belief that is often reflected in form (and software/DB) design.

[umanwizard]

I would describe the issue here, though, as "Federal government believes everyone has a USPS address (mailing and/or physical)", as opposed to "local political divisions within a state are particularly meaningful to the federal government".

The thrust of my point is the same -- the feds don't ask you to write a city outside the context of an address. The fact that they assume addresses exist is a separate issue, IMO.