Because doctors get paid by the syllable?
So What's Going on Here?
The pharmaceutical industry is fond of taking conditions that were once considered a normal (if annoying) part of life and encouraging the use of their clinical names. Why? Probably because the use of "medicalese" results in people perceiving a condition as more serious and rare, which in turn leads to a shitload more frightened potential drug buyers. That's right: All you have to do is start calling male pattern baldness "androgenic alopecia," and all of a sudden people will be clamoring to run marathons for it.
But this psychological effect also works the other way around: Some diseases currently don't sound serious enough to our easily manipulated brains. For example, there's an initiative being pushed by the Rheumatoid Patient Foundation to rename rheumatoid arthritis, because they claim that calling a systemic autoimmune condition "arthritis" hampers research funding and insurance coverage. So, your medical condition getting insurance coverage might be seriously affected by the stupid name someone gave it in the past. Here's an idea: Let's just start calling all diseases "-rot" (joint rot, brain rot, dick rot, etc.). That way, they all sound equally serious and insurance companies will have no language-influenced reason to deny coverage for treatment.