In medicine, the primary goal is to help, rather than understanding why something works exactly. Sure, understanding is an important goal too, it's just much harder to achieve than being able to help. And less important than knowing that your treatment will work, without any major side-effects, for the kind of patient in front of you.
Taking an extreme example to illustrate the point, if you could image every atom in the body you’d have the opportunity to understand the whole-system dynamics, or try to isolate subsystems if that helps.
> In medicine, the primary goal is to help, rather than understanding why something works exactly.
Right. My point is that each phenotype is different, and so understanding the individual will allow you to help them more.