Since in traffic conditions a motorcycle can reach its destination quicker than a car the purpose of the moto ambulance is to provide the initial assistance while the car arrives.
We here in this third country world have moto ambulances as well, at least in Bogotá the capital city and in the nice Medellín where I live, however here smaller machines are used, I have seen Suzuki DR650 and DL650, the last one definitely not as smaller.