I think that is a crucial difference morally, legally, and politically.
It is one thing to give up your own autonomy because you don't trust yourself, which is entirely reasonable.
It is another thing to give up everybody's personal autonomy because you don't trust yourself.
Giving the government the power to strip someone's rights and place them in guardianship I'm sure avoid some elder abuse and suffering.
My point is that I don't think it is ethical for those who want this protection to make that decision for everyone.
Every day people do lose the ability to make informed decisions without preparing for that change. How and why we respond to that doesn’t change the underlying biology.
How many many benifical guardianships are an acceptable trade for one abusive guardianship?
Maybe the answer is absolutely 0 and this should be off limits for policy.
To be clear I am not saying government is the right solution, just that the problem does exist. Not just because people get taken advantage of but because taxpayers gets stuck taking care of people who have lost everything.
PS: Being able to trust children is one solution that works at the individual level, but it unfortunately doesn’t scale.