Why Don't People Use Formal Methods? (2019)

I saw this question on the Software Engineering Stack Exchange: What are the barriers that prevent widespread adoption of formal methods? The question was closed as opinion-based, and most of the answers were things like “its too expensive!!!” or “website isn’t airplane!!!” These are sorta kinda true but don’t explain very much. I wrote this to provide a larger historical picture of formal methods, why they’re actually so unused, and what we’re doi