At least in the US, the regulatory framework and medical system is heavily biased towards mass-produced pharmaceuticals. Biological agents like phages have a m

At least in the US, the regulatory framework and medical system is heavily biased towards mass-produced pharmaceuticals. Biological agents like phages have a much higher regulatory hurdle to clear (you need to show that they won't develop virulence), and they have also been traditionally harder to administer than drugs (e.g. phage therapy ideally requires a sample of the infectious agent and individualized identification of phage species). Basically once we discovered penicillin, it was so cheap, effective, and easy to distribute, that we built a medical system premised on developing new drugs, and dropped most alternatives. It's very hard to turn back the clock. FYI, one reason phage therapy continued to be developed in Eastern Europe was less widespread availability of antibiotics at the time.