One of the commonest fallacies that we carry over from everyday life, over to chronic disease is that early detection followed by intervention will reduce the burden/discomfort/work in the future. We are probably wired for this fallacy, for example in the prehistoric era: detect an impending attack by an invading enemy would have resulted in better survival.
Some non-main stream cancer practitioners postulate that the only reason cancer survival rates seem to have improved over the years is because of earlier detection. A cancer survivor is broadly defined as someone who lives 5 years after detection of the cancer. So in the distance past when detection methods were relatively primitive cancer was detected at the later stages and the patient died quickly there after. Now they live longer after they have been detected because it was detected relatively earlier. The better survival rate is attributed to the treatment regiment, which is not the case. It is just that the window of time between detection of cancer and death of patient has increased.
Anyways, none of this is news to people are understand human nature, there is quite a bit of 'superstition' even in science and medicine.
If I decide to let the disease progress to the point where I don't know my family members and am acting violently, how likely is it that a cure is going to be found that can reverse that damage? I don't think it's very likely and so I would probably choose to die before that point.
The current time from diagnosis of Alzheimer's to death is about 8 years (with some variability) with a relatively slow progression of symptoms. It's possible that some people may want extra time to make arrangements like you say, but this comes at the cost of living without knowing whether you have Alzheimer's. I've never been in this situation, but I can't imagine that this tradeoff is clear-cut for anyone.
I think my gripe with the article is that it claimed this test will "promptly be used clinically". I seriously doubt this. The article doesn't report the sensitivity or specificity of the test, and we don't have a great sense of how early this test can detect Alzheimer's.
It's difficult for potential sufferers of Huntington's Disease to decide whether they want the test. Some do and others do not, but most potential Huntington's Disease sufferers are happy that the test is available.
Until we have better cryopreservation
1. Because people want to know for lots of reasons like financial planning or "bucket listing".
2. The more people who know sooner, the more we might learn about the disease, how it progresses,
and the genetics of the people who acquire it.