Ada is like Smalltalk or Lisp at this point. It's not new and shiny. It's not being marketed. It's seen as outdated, or even extinct (how many people know an Ada developer or project)? Like it or not, people bandwagon technologies. Not to say anything against Rust, Go, etc. But how many people who have jumped on one of those bandwagons did so after examining Ada, and found it wanting in comparison, do you suppose?
There's also the expectation that a more modern language will have modern tooling people today need, and community support easy to find (if it's caught on).
There's also the expectation that a more modern language will have modern tooling people today need, and community support easy to find (if it's caught on).