I am afraid I can't totally agree Stanley.
Well, there's a surprise!
You are just repeating the underlying view of all the main political parties which is that 'nothing can be done' as any change would be too expensive. Fortunately, in the coming election some of us will be able to vote for a party with a more enlightened policy.
I expect you're right about the Attlee government's reasoning way back in the mid-twentieth century and, incidentally in a period of unavoidable austerity, but so much more is now known about conditions like dementia (though not nearly enough). I'm sure a distinction between 'frailty' issues and problems caused by dementia could be made today, though personally I think frail people who need help to stay as healthy as they can be should be cared for.
I notice that you give no examples of the other illnesses which you say are in the same category as dementia. Perhaps you could do so.
To clarify, someone who is in danger of dying because they have a damaged heart does not have to pay to be kept alive. Why should someone with dementia have to pay to be kept alive (I know some people would ideally like to be euthanised rather than kept alive, but that's a different issue)?