I think you raise a very good point, Silverbrooks..
I have helped many people to complete PIP claim forms or to challenge PIP decisions, but my task was to help them explain how they met the criteria, not to judge. I only ever met one person who I felt would not qualify, though I knew from experience that some would not be successful.
Most did not really understand the criteria or how they might qualify.
I often wondered ( privately) how they would use the money, as the majority did not seem to have specific financial needs - or no more than anyone else on a low income. This leads me to think that the basic Universal Credit is insufficient to cover the basic needs of anyone not in work. I think many people rely on PIP to pay the bills, especially heating bills, rather than to pay for care costs, or for help around the house.
Of course, the most severely disabled have great needs for special equipment, additional care, particular food or clothing, but their claims are not in any doubt.
So whilst I am not at all happy that the country’s deficit should be plugged by claimants losing entitlement to benefits by tightening the criteria, I do privately find it hard to justify the high cost of benefit claims, when their ( undoubted ) illnesses and disabilities do not actually generate specific higher costs.
I can certainty see the value of measures to help people back into work, but before that can happen, they need more medical help, especially psychiatric help, or long overdue operations and other treatments to improve their health. Otherwise they will not be able to hold down a job.