because you can't tell until the damage has been done, which ones are good (And yes, I do know many of them are very responsible)
However, even 'some' good dog owners with friendly dogs with exceptional behaviour could kill my nephew.
He has an allergy to dogs which is potentially fatal. He has been hospitalised a couple of time due to his reaction (inability to breath).
Why can't ALL dog owners, even the good ones keep their dogs away from other people as a default?