This is my guess also. Even in large engineering-driven companies, you often discover during your very proud (internal) talk about Shiny New Tech that other people in the group have been doing it for some time...

But you never know, maybe I looked in the wrong parts of the Internet.

I'm genuinely curious though: since most of those projects are open-source you'd expect to see some traces of some activity/problems on GitHub or on mailing-lists, and... well... Not much to be seen.

I've seen some rare papers with CBMC and I know the tech has been ported to Java, javascript and apparently something is in progress for Ada ?

angr I tried very hard to use on Ada programs but it seems the VEX lifter and CFG builder couldn't handle simple Ada programs (wasn't patient enough to submit this on GitHub...). But for C programs it's very fun and all scriptable ! There is also this nice of a 'pluggable test environment' (deepstate from Trail of Bits https://github.com/trailofbits/deepstate) that allows to switch between hand-written unit tests, fuzzers, and symbolic execution (letting you decide which variables are Symbolic, which are concrete...) with angr. Also some cool stuff mixing AFL and angr (driller) and another project mixing Intel PT and angr.

KLEE seems to have the most papers (quantity and quality), just landed support for C++ and upgraded to a recent llvm...