It's because health insurance companies need to pad their profits. Because we have a backward system in the US where profits are extracted by everyone without any competition from a not-for-profit. That's why the idea of a public option is so popular (it was originally a Republican idea until it was decided insurance company profits are more desirable). Personally, I don't think any health insurance company should be for-profit. But the for-profit companies sure as hell should have a non-profit competition with the same bargaining power they do.