Because many diseases, like arthritis, vary in severity from patient to patient. There are many subtle variations in arthritis symptoms that are not measurable by tests in a doctors office. Having a variety of treatments to try gives patients a chance to find out what works for them.
Those treatments are “standardized” in the sense that they are mostly checked and approved for safety. Of course, there will always be some (nontoxic) snake oil on the market like CBD cream.
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