Why can doctors be so incompetent?

> Nowadays you'd have to be declared dead from the neck up to consider "Heroin Cough Syrup for Kids" a good idea, but a mere century ago, that was the shit 9 out of 10 doctors were recommending.

I got prescribed "Hydrocodone cough syrup" for cystic fibrosis cough from age 13 until I wised up and stopped talking to doctors about it. This was ~30 years ago; I have little doubt they'd do the same today.

For clarity, my choice is cough stuff up or drown on it. Doctors seem to prefer "drown quietly".

Until 50 years ago, one could purchase paregoric (https://en.wikipedia.org/wiki/Main_Page) without a prescription. I got a spoonful or two many winters of my childhood.