They are banned in Ontario, Canada for a good reason and banned in UK for the same reasons.
The only time my dog was ever randomly attacked was a pitbull and you quickly learn talking to other dog owners how common this is. Nothing clears out a dog park like a pit bull showing up.
The ban isn't meaningfully enforced in much of the province [1], I see them a lot. I used to live in Ottawa, and their official site directly states "The City of Ottawa does not enforce the provincial ban on pit bulls" [2]. For those (legitimately) interested in a Canadian perspective on breed-specific legislation, there's a documentary by CBC's Fifth Estate on the subject [3].
Yep, that's why my dog still got attacked by one in Toronto. It's poorly enforced. The dog sprinted across an entire field without making a sound and pinned my dog hard by the throat.
Ontario also tried to remove the pitbull ban, after the usual "it's owners the owners" protests, but a bunch of attacks happened again so they reinstated it.
I suspect the reasons are (generously) keeping them out of the hands of people who would treat them poorly and perpetuate the stereotypes, or (less generously) ignorance and fear.
There are plenty of statistical studies out there that pit bulls specifically cause both a significant plurality of dog bites and significantly worse injuries than other dog breeds.
The word "pit" in "pit bull" refers specifically to a dog fighting arena where dogs are supposed to aggressively fight each other in a duel, possibly until one of them dies.
"pit bull" refers to a dog breed that was optimized for its performance (=more aggressive and dangerous) in the "pit".
How they're raised makes a big difference, but natural instinct is natural instinct. It's just like how chihuahuas were bred to be small, but pit bulls were bred to fight other dogs.
The only time my dog was ever randomly attacked was a pitbull and you quickly learn talking to other dog owners how common this is. Nothing clears out a dog park like a pit bull showing up.