> most devs don't want to do formal verified system development.

That may be true. Serious question though: even if most devs wanted to develop formally verified code, do you think that it is reasonable to suggest that the typical systems developer could do it with today's tools? I don't mean verified protocols (TLA+) or verified algorithms (SPIN) I mean end-to-end verified code, a-la seL4. I got the impression that this is still very specialised work. Perhaps things have advanced since I last checked.