We still seem to engage in the "but mind is completely different from body" pattern of thinking.
Even if the modern reincarnationists were right and brain was just a TV set channeling the mental "signal" instead of the source of your mind, it is pretty clear that a broken brain is usually part of a broken body. Degraded metabolism, stiff arteries, cancers, most such pathologies involve the entire organism.
It’s not that it’s completely different, it’s that we have an extremely limited understanding of the brain and how things operate.
Things like CTE can only be diagnosed post-mortem, so research on those things would slow significantly (unless people who got it killed themselves like others have).
I am specifically speaking to head trauma, mental disorders, and issues with the brain. Things we don’t know how to treat or fight, that a 30 year old body would only serve to prolong the pain and decline caused by the illness.
Even if the modern reincarnationists were right and brain was just a TV set channeling the mental "signal" instead of the source of your mind, it is pretty clear that a broken brain is usually part of a broken body. Degraded metabolism, stiff arteries, cancers, most such pathologies involve the entire organism.