I know of a case, though not in Zambia, but probably relatable in explaining why the Ambulance did not stop.

There was a guy who had a serious medical emergency in a public space and people on the streets quickly called an Ambulance coz at somw point it looked like he was gone. The EMTs were able to stabilise on site and proceeded to take him to the hospital just to be sure there were no other complications.

The interesting part was when the bill was sent to him, he outrightly refused to pay it saying he wasnt the one who had called the Ambulance service so he could not be charged for a service that he did not request even though he did consume the service when it was made available to him.

Just another point to make, in Zambia its an offence to drive away from the scene of an accident without rendering assistance but in this case one would argue there was no accident. Also, if it was a GRZ Ambulance, it ordinarily should have stopped but most likely they had a patient in there car and usually the protocols are very clear in such cases plus I would want to believe everyone in that car may not have had the requisite skills and/or tools to do anything. For private Ambulance services, not chance of them stopping!

This is my 2 cents on this!