You have too look at the big picture though. How much time would have been needed to train the PhD student (might have been even the PI) to write more maintainable code 10 years ago, and maintain that code to "best practices" over the time, compared to write that it works once and need to rewrite once after 10 years?

Moreover, people tend to forget that scientific software evolves much more slowly than commercial software and the number of people who work on this are much fewer, so why always adopt the newest method, if the code is still working. Show me commercial projects that have had the stability of something like LAPACK or BLAS, those essentially had a stable API for > 50 years now, with very few bugs.