Very often, pill formulas are not stagnant, especially those ancient ones passed down through generations, which have experienced constant modifications and enhancements, changing considerably compared to their original versions.
This could be due to various reasons. Sometimes, a particular medicinal ingredient used might have become extinct and hard to source, thus requiring a substitute.
In other instances, better medicinal ingredients might have been discovered so as to make the pills more effective.
In sum, it's often necessary to be flexible in pill formulation. The ability to replace the original ingredients in a pill formula with others is a fundamental skill that many Pill Refiners need to possess.
However, for the majority of young Pill Refiners, they don't possess such profound experience. Put plainly, their basic skills are not solid enough.
Without years of trial and experience, they would not dare to attempt such a thing.
