Well if law abiding citizens are obliged to use their assets for elderly or other social care, and are penalised for giving it all away whilst alive as in depletion of assets, why should prisoners not contribute also for their care where they can afford to?
Otherwise, it would make sense for elderly infirm etc. to just commit a crime, and be kept at Her Majesty's pleasure, and their assets remain intact for their heirs.
Sorry, that's a controversial comment I know.
But I actually don't know what happens if a person of means is sent down and then dies whilst in prison either. Interesting question.