Lots of reasons but I'll list two: 1) These documents are historical artifacts like the declaration of independence or the magna carta. They may not seem import

Lots of reasons but I'll list two: 1) These documents are historical artifacts like the declaration of independence or the magna carta. They may not seem important now but in 300 years people will care about them A LOT. 2) Redundancy. If the digital records are destroyed or say encrypted in a massive ransomware attack then the UK government can simply reconstruct those digital records using the paper records without having to deal with terrorists and that's a good thing.