Unit testing should be just a natural part of the code development workflow, just as the compiler is.
However, this requires educating the management on the benefits of the unit testing. Junior developers have relatively low chances to have such influence, though. Thus, whether a company is a proponent of the unit testing depends on whether they have a senior developer or architect that is an advocate of unit testing.
I believe this is the answer to your question "what's missing and why aren't more companies doing unit testing". :-)
