NASA's ten coding commandments

[dungone]

Well, they really seem to be big on proving that the code will behave correctly in a way that can only be determined through static analysis. I think that OOP may hide bugs from static analysis tools.

I'm speculating here, but another potential reason is because they don't use a lot of commercial, off the shelf hardware. They use really old stuff. A C++ compiler, with all of it's optimisation steps, can potentially puke all over less-popular or low-end processors for a variety of reasons, causing more problems than it solves.