Great post, and i couldn't agree more. I'm in healthcare and it's shocking sometimes how little is known about "wellness" compared to physiology, pharmacology, etc. Hopefully this will change...
The issue (apart from capitalism) is that medical knowledge was empirically established by trying novel (and reactive) treatments on very sick people and seeing what happened over time. A lot of medicines/surgical procedures work to help people escape dire pain and suffering; these have been established because it is a lot easier to measure these effects objectively.
It is a lot harder to measure and control for the little lifestyle modifications (that surely have benefits for many) in a objective study that convinces skeptics and allows them to confidently prescribe such measures with the knowledge that it is going to benefit the patient in a defined way. This is further muddled by individual variations at every level from epigenetics to vascular anatomy.
Our perfect hindsight is so bittersweet.