[tjr]

I presume that most payphones (in the US, not sure about elsewhere) have been taken down because real numbers showed that they weren't being used enough to warrant maintaining them.

But sure, I think it's reasonable to expect some people, sometimes, will still need to make use of a phone other than their own.

Also: what about phone booths? Even if there is no phone in them, sometimes holding a private conversation in public on a mobile phone can be awkward.