I think people that live in "nice" areas struggle to understand how lawless certain parts of the country are.
Several of the attacks have involved people that were already breaking the law in some respect, eg this one had a bully illegally rehomed as did some of the others
Often the co-hort of people involved in attacks aren't going to sign their dog up to anything
Part of the reason I wasn't for the ban was because I felt it would be useless and not enforced. Decent owners will comply but their dogs are usually not the ones involved in things like this
Where I live recently there was a massive bonfire that caused damage and was really dangerous, police saw it being built and did nothing. Residents hurled things at fire brigades, and ultimately blocked the road off so no emergency services could attend, while crowds of people watched.
These people aren't going to register their dogs because they were asked to, the police aren't going to attend to check