I work in emergency services. Your argument works for rural areas that are far, far apart. I do timings for station to suburban homes and the like, regularly. You're just not correct on this at all.
The best hospitals in my town's metropolitan area are _inside_ the city, not in the suburbs. Maybe there are some good ones where you live, but ambulance timing is not the only factor—the quality of service is just as important.
I’m curious what you think the ED outcome difference is between the best hospital in your city, and any random suburban one, for generally common emergencies.