Scotland's devolved government has just announced laws to control the poorly-defined "American XL Bully" breed of dog, England having already done so (I am not sure about Wales and Northern Ireland).
This strain, I think still not defined and recognised by the Kennel Club, was bred to be dangerous by default. With the kindest care and training in the world, any dog can attack other animals including humans; usually unpredictably, but unlike most recognised breeds this is one is specifically aggressive and unstable. Individuals of it have already killed at least two people in England.
So it is now illegal to breed new ones, or to import, sell, give away or abandon existing ones. They have to be kept very securely, and must not be un-muzzled and unleashed in public. Predictably Scotland's wish to differ from England created a delay allowing it to become a re-homing destination for the creatures; as its own Parliament has acknowledged.
Just why are such animals bred? Obviously money for the breeders, if there is a market for them, but for what sort of owners?