The UK is more or less unique in not having a national register (of people) and this makes it impossible for people to have a recognised residence on record and, conversely, anyone (including the authorities) to know where to formally contact people (officially).
Credit rating agencies are therefore at a disadvantage when asked to rate a named individual and they have come up with the electoral roll as a (very poor) alternative.
In another way the credit agencies are in a uniquely advantageous position in that, (I understand) unlike any other private entity or individual, they get access to court records. The fact that the court system sells the records to the agencies is good reason for criticism of the system. In some other countries anyone can access the full records (excepting very sensitive cases, such as adoption, etc.) on the internet.