Aside from the "ego" aspect that was already mentioned, western science and medicine seems to seek "the one true answer". Western medicine pretends that all bodies are identical.

In reality, this would mean that everyone has the same metabolism; the same flora, fauna, and fungi in their digestive system; the same release ratio of all hormones.

Since the populace is innundated with this "all bodies are the same" concept from the medical industry, they often don the same hat without realizing it.