Well you're right but the idea of getting all of the DNA information is precisely to be sure to not rely on what we think we know, so that if in the future we d

Well you're right but the idea of getting all of the DNA information is precisely to be sure to not rely on what we think we know, so that if in the future we discover that previously thought useless parts are meaningful we would already have them in store (gathered long before the DNA gets damaged by age). Once we have everything, we can apply additional knowledge to this data as soon as it is discovered and without needing to do more sequencing.