You know how we have age limits for different things, because we know that the brain is an evolving organ that changes over time? Like, we don't trust that you can drive without hurting anyone consistently until after a specific age, etc.
Well, the brain don't just develop for the better over time. After a while it starts deteriorating. That's a fact. It happens to all of us. At different speeds, yes, but that's true for the positive development too.
So why don't we have upper age limits too?