It's a complete lack of understanding of, and care about the concept of risk, and of critical thinking generally... along with poverty (both material poverty, and poverty of aspiration) and of being able to 'buy in' to being a 'someone' where the barriers to entry are low.
- Will my XL Bully attack someone?
We don't know, maybe.
- If my XL Bully attacked someone, what would the consequences be? Again, we don't know, but highly likely to be catastrophic or fatal.
A lot of people can't conceive of both 1. AND 2. at the same time, or they don't even consider 2.
And people don't really understand the concept of death being the end. I'm sure they think... It's only a nip... It couldn't happen to me/my kid... I'd call an ambulance. They don't realise that death is potentially terrifying, grisly, quick and final.
See also: people who ride unregistered trail motorbikes like maniacs on the roads and other places they shouldn't be.