Why is that weirder? The people writing scientific software are, by and large, less good at writing software than people who only specialize in software development. I’d expect there to tons of terrible engineering practices in an old code base like that
In my time looking for published papers, I have only very rarely seen papers which are also hosted by the university of the author. I suspect in your case it was hosted because of something specific to the school or the author, rather than a general thing.
What I am seeing more often in my field is people posting a version of the paper on “arxiv”. This is a similar open-access approach, but you do have to be careful with arxiv papers as you can post anything on it, including work that never was or will be peer-reviewed.