Have you tried explaining it to them in exactly the way you have written it here? What was their response? In my experience, this happens quite often with peop

Have you tried explaining it to them in exactly the way you have written it here? What was their response? In my experience, this happens quite often with people coming from academia because they're used to write throwaway code that doesn't get read by others and doesn't need to be maintained. It's only used temporarily to publish papers. However, most of the people I have worked with were aware of the fact that their code didn't follow software engineering best principles, they just didn't know how to do it better. Another factor may be ownership. Sometimes people are excited to implement something because they like the idea of owning part of the stack, e.g. the caching implementation, instead of constantly implementing minor improvements in other people's code. Perhaps these people are looking for ownership of something more so than a specific complex solution?