You can have a non-life threatening injury that prevents you from operating a car yourself, and without access to something like Uber or having another person to drive you, could necessitate calling an ambulance.
(Though the wording of the GP was slightly ambiguous and seemed to compare a time-sensitive emergency to being able to take some other vehicle to the hospital)
A study was done (I haven't read the whole thing) that seemed to indicate cities with UberX had a reduction in ambulance use: http://www2.ku.edu/~kuwpaper/2017Papers/201708.pdf
(Though the wording of the GP was slightly ambiguous and seemed to compare a time-sensitive emergency to being able to take some other vehicle to the hospital)