Part of the neighbour problem (someone, in Wood Green I think it was, was found to have died 3 years before folks broke in. The rent etc was being paid automatically from social services) is that people are more mobile and interact less in the community. They regard the flat etc as just a base from whence to go to work, to socialise with workmates... It's most unlikely to meet a neighbouring flat dweller by chance and there are no garden walls to chat over.