The time to downsize your house is when you still feel you don't need to. I know from personal experience of relatives and friends that by the time you really need to it's often the case that your physical and mental health isn't up to it and the upheaval is too much. No government would ever do it but they should incentivise downsizing more. It might save money on carers allowance and help people stay in their own home rather than end up with the council paying for their care.
If you have a property to downsize from, it is unlikely your care will be funded by the Council 😊
Otherwise, from personal experience, I would agree. ie when you are capable of downsizing, you dont want to. When you need to downsize, you aren't capable of it. 😂
I was instrumental in one downsize exercise, which, so far has worked out well, in terms of quality of life, if not necessarily finances:
My brother-in-law lived at home (3 bed semi detached, with large garden) with his parents, until their death.
He is what would now be called "SEND", although, he did have various low skill, low pay, jobs, during his working life.
Initially he managed reasonably well, I organised his finances on his behalf, ordered his groceries on-line etc. However, day to day chores, especially the garden, soon proved too much for him.
We organised for him to downsize to a "sheltered accommodation" where he has his own apartment, "grounds" are maintained by a service company, as are "shared spaces". There is a warden system, with emergency call facilities, for his safety. It is still necessary to organise his finances on his behalf, and, do his grocery shopping online.
On balance it has worked out well, he has even teamed up with fellow female resident!