Make it make sense - US healthcare

I have become severely anemic since my thyroid was removed. I need an iron infusion because my iron stats are in the toilet. A 5 which is incredibly low and explains my fainting spells. I’ve not met my deductible yet for my insurance through my employer which and then wanted 3k for my infusion so I had to cancel that because I don’t have that type of dough laying around. I don’t understand how my insurance would rather pay a hospital bill than an infusion because that’s what’s gonna end up happening. 😔