There's still money licensing Fortran libraries that have been around for decades. They are fast and good and cheaper than achieving the same levels of fast and good from scratch. There's nothing intrinsically wrong with using some gem written over a weekend of craft beer. It just may not make sense to bet a business on it even when you can read the source code

StackOverflow is an example of why the choice is beneficial. The source code being proprietary is irrelevant because the content is Creative Commons.