There a few many reasons why plastic bottles aren’t the best option for some medications and it comes down to the technical specifications of the drug as well as drug safety regulations.

Iirc, bottles aren’t optimal for formulations that result in friable (brittle) tablets, or those that need to be packaged in a reduced oxygen environment so that you can take out a tablet individually without exposing all the others to regular air, and so that they’re easy to handle and transport individually without exposure to contaminants in the environment up to the moment that they need to be ingested.

I encourage people to look deeper into pharmaceutical technology. It’s a fascinating field full of surprises.