I think it's hard to justify a young, low-earning couple, perhaps with small children, having to contribute to the care costs of someone in possession of property worth hundreds of thousands of pounds.
My MIL needed care at the end of her life. None of her children were willing or able to do the task so her care was paid for out of her estate.
My mother is still living unassisted in her own home, at almost 90yo, but should she need care, we, her children, can't/won't do it so I'd be only too happy to pay someone else to take on the task, and if that costs us an inheritance, so be it.