Who still uses payphones?
No distinct demographic identifies what class of people uses payphones today. Anybody can lose a cell phone or have their battery run out, potentially necessitating that a call be made from a public telephone.
In other circumstances one might want to use a public phone for its veil of anonymity.
Some cities have actually seen an increase in emergency 911 calls being made from payphones. This seems to mean that people have wised up to the fact that reporting a crime from your own phone comes with the risk of being associated with the crime being reported.
Many underground subway systems are still without any form of wireless connectivity, potentially making payphones an option when one needs to reach somebody above ground.
The conventional wisdom that only drug dealers and guttersnipes use payphones does not stand up to logic, nor to evidence: The Payphone Project’s series of photos showing People Using Payphones illustrates that most any type of person can be seen using payphones today: young, old, well-dressed, not-so-well-dressed.
New York is exceptional, though, in that its relatively abundant payphone population (about 7,000 as of Summer, 2014) attracts more usage simply on account of being there.
Payphones tend to get attention during disaster situations. In the wake of Super Storm Sandy New York City saw long lines of people waiting to use payphones in lower Manhattan. The east coast blackout of 2003 saw similar lines at payphones, as I recorded in this Blackout Payphone photo.