I don't know about this.
The most likely dog you're going to be attacked by is a jack russell, but it's not going to kill you.
I've had rotties, alsatian crosses, staff crosses, and now I've got a toy poodle cross (very nippy little chap); but my daughter (33 this year, married long time, has a kid) owns two really big Boerbels, before that she had an American Bully, and before that she had a Dogue de Bordeaux, and before that a staffie.
Why? Guard dogs. She works at the worst end of child protection as a social worker. Her clients are terrifying. And County Lines is ripping a hole in our communities, especially the most vulnerable. It's not hard to find out where someone lives. As it goes, you can see that she and her husband are experienced with large breeds.
I think the question should really be why are people willing to dice with death? What are they so frightened of that they'd rather trust an animal with a brain the size of a pea over actual human communication? Well, I found out recently at school. Kid who was being evicted so that she could live in a car (yes, a car) had a Chow to defend herself. As someone else says, these dogs get passed around, it's not just about the money, instead a sense of deep desperation. Difficult to 'cherish' and 'care' when you're 14 years old and living in a car.