Dangerous dogs

Over the last few days we have heard the terrible report of a young girl being brutally killed by dogs.
2 mastiffs and 2 staffordshire bull terriers.
You cant even begin to comprehend what happened to that poor girl and rightly so the dogs have been destroyed but and its a big but why are the owners not being prosecuted.
I have a Staffordshire Bull terrier and she is a huge softy just like the one we had before her but we know what she would be capable of the same as any other dog.We as responsible dog owners and Lexi is on a lead whenever she is taken out of the house.She would never be allowed to be left in a room alone with a child as nobody can anticipate what reaction any animal would make if something nasty was done to them,one to many pulls of your ears etc.But what i do know is that Staffs aren't all bad they are actually recommended by vets as an ideal family pet,my vet has one.We don't teach our dog to play aggressively she would much rather roll over in submission and have her belly rubbed.
I would take full responsibility for my dog and wouldn't put her or us in a vulnerable position.