I agree with you that the scientific community is way behind industry standards, but the reason for that is much less of their code is actually designed for reuse. The overwhelming majority of their work is just "let me try writing this code and see what results I get."
Industry professionals are forced to take the approach of "I need to write this code to be as maintainable and flexible as possible" because they have no idea what the business is going to want next and generally have no set timeframe for how long they may have to maintain any particular project.
A lot of industry code is also glue logic which doesn't express any original idea which makes it inherently easier to document. Code expressing a novel algorithm is never going to be as easy to document and maintain as code plugging standard libraries together. Notably, code in "industry" which does express novel algorithms is often also not so easy to read, there just isn't that much of it on most projects.
There are efforts to integrate more industry standard software engineering practices into research (RSE or "research software engineering" as a phrase is growing in popularity):
Industry professionals are forced to take the approach of "I need to write this code to be as maintainable and flexible as possible" because they have no idea what the business is going to want next and generally have no set timeframe for how long they may have to maintain any particular project.