Because there's a push for insulin affordability, and they look really really really terrible when someone brings up a chart of the rise in the price of insulin over the past few decades.

https://divabetic.org/2017/06/08/transparent-pricing-works-h...

They fear a Congressional inquiry and federal price caps. Normally, you'd expect a new medicine entering the market to get cheaper as the production ramps up, yet it's gone the opposite direction, even after the patent has expired.