There are many people in that ecosystem, who are not primarily software engineers. Some just learned some coding along the way. Some are mathematicians. Some are devs who are AI drunk or something. Some have the mindset of "code doesn't matter any longer, if it works it works". For many proper dependency management is just a chore, that they don't want to care about. These things come together in various ML projects, even though ML projects should be amongst the projects most focused on reproducibility.