As one who has spent half their professional life working in South America, speaks fluent Spanish and Portuguese and had dealings with the civil aviation authorities in most of those countries, I will say only this:
1) Not all of the accidents which take place are investigated or reported officially. Example - the 'meat run' from Trinidad (Bolivia) to La Paz when there were many accidents, one of which I saw myself, but it was never formally reported.
2) Why were DC-3s allowed to take off from Villavicencio (Colombia) with their doors removed so that they could carry petrol drums? This happened in plain sight during the day - I saw it with my own eyes - and not just once.
I fully understand that breaches of the rules take place in other parts of the world too, but I speak only of what I know.
So lack of regulation then?