I'm sure that Luckygirl is right, it would be more expensive to means test for many of these benefits than to pay them to all pensioners.
My daughter is long-term disabled and at one stage did not pay council tax, but now has to pay a discounted rate which is far more than she could afford, so the Bank of Mum and Dad have had to take it on for her. I should add that she is constantly reassessed for her benefits and the forms that she has to complete are very long and fiddly. At one stage she got help with them and advice on all her problems and difficulties (for which she had to pay from her benefits) but now she gets less benefits and no help from anyone. Except advice from a nurse when she goes in for her regular injected medication who seems to have advised her that she would be better off not seeing us at all. Perhaps the nurse is willing and able to take on our role, involving both 24 hour telephone support and financial support?
Sorry, this has turned into a bitter rant!