First, they do. Second, most software is not only not produced by software startups, it's not even produced by software companies. Do you know how much software a bank, or a credit card company, or a telecom provider, or a car manufacturer (like BMW), or a shipping company (like FedEx), or a defence company (like Boeing), or a large retailer (like Walmart) write in house?
Wasn't the discussion about greenfield projects? Or by greenfield do you mean internal greenfield projects at existing companies that already use Java?
i can't speak to the others but banking and healthcare is virtually all java top to bottom. The big healthcare EMR/EHR systems are Java and every bank i've ever worked with (i use to do a lot of integrations with the big banks) was all Java. I have friends in those areas and whenever they start up a new project it's still always Java since that's where their skills are and what's on the "approved tech." list.
Until quite recently, the reasonably feature complete open source libraries available for things like DICOM or HL7 were old C/C++ libraries, Java, and C#. That often created a choice between Java and C#. People not doing Windows based development tend not to be interested in C#.
We embedded angular in our old Java client for hospitals. The user thinks he just opens a new window, but it's chrome in Java, which opens angular frontend, for our Java backend.
