The kidney's evolutionary design prioritizes reabsorbing beneficial substances from initial filtration over identifying and eliminating harmful ones.

“one of the things that I recall being sort of blown away by in medical school was how smart the kidney was you don't think of it as a particularly intelligent organ you think of it as well it's just a filter but there was a very clever design in evolution which said rather than the kidney learning what is bad and figuring out a way to always get rid of things that are bad it was the opposite it was learn what is good and when you throw everything out during the first pass of filtration just learn to pull back the good because the probability that the good things are gonna change is low the probability that you'll see new bad things is high”