There's all sorts of GDPR nonsense involved in chasing people and firing letters off to addresses where you think someone lives. Granted a lot of folk don't realise they're entitled to a pension, the majority would be short term service who left in their '20's. That gives them almost 40 years to forget their entitlement and lose their discharge paperwork. It really is down to the individual to take charge of their own affairs; should they do so then the money is there.