[ThrowawayP]

While I don't directly agree with jrs95, the fact is that the pills just plain don't work a lot of the time. Google the medical term "treatment-resistant depression". The very first link says "Despite advances in the understanding of the psychopharmacology and biomarkers of major depression and the introduction of several novel classes of antidepressants, only 60%–70% of patients with depression respond to antidepressant therapy." (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3363299/) Presumably, the odds were worse before.

Consider, too, that that probably doesn't even include those that develop tolerance effects afterward; with that, the numbers likely climb much closer to 50%-50% or worse.