Here is a real example, around 12 years ago, I reviewed code for satellite control. The code was in C++ and using CORBA running on a distributed system to control a constellation of satellites. The code was for sending commands to and processing telemetries received from satellites. The guy was an old timer who knew inside-and-out about controlling satellite. However, he wrote FORTRAN most of his life, and now he had to do C++. He has a switch statement contains almost hundred of cases. Terrible code, almost non-maintainable, but functionally correct. So the only thing I recommended was based on our coding style guide, this should had been rewritten. However, that would cause a major redesign and retest. And that code I believe is still running as we speak.

Unless for people who write software for programmers, like compiler, or OS, or some middleware, most programmers write software to solve some problems related to problems other than computer. These people may very well be electrical engineers or aerospace engineers. They aren't really trained to design software. They will have the biggest problem adopting OO. There is a whole lot a software architect can do, because the resistance from below. It may be bad for software people to work in this kind of environment.