@Missamyp
The annual total of unclaimed income-related benefits and social tariffs is now approximately £19 billion.
Perhaps the potential recipients don't actually need it! I'm sure that most people in genuine "need" will be getting the help they need to claim. After all, there are all kinds of people and organisations out there telling people what they're entitled to and helping them claim.
When my OH was diagnosed with cancer, he was given all kinds of pamphlets about how to claim benefits, plus a specialist cancer nurse who talked him through rights such as free hospital parking, help with travel costs for treatment, at what stage he'd be eligible for carers' allowance and PIP etc.
My MIL has dementia, she'd had two different people go to her house after first diagnosis, helping her to claim carers allowance, blue badge, talking through PIP, asking about her income to see if she was entitled to pension credits, etc.
A lot of people who are entitled simply don't want to claim because they don't actually need the extra money and they don't want the hassle of going through claims' procedures, hassling the GP for proof letters of illness, etc.