I also find this annoying, but it‘s common practice to do this while a draft is still being worked on and not yet getting submitted to a journal (SSRN is ≈ SocSci Arxiv)
I can see for example if its' mostly word documents from source on that area of science maybe there's no point on arxiv like pipeline that builds from source.
wondering if it will ever converge there, like a wikipedia only about science/research but of all areas
Part of the issue is that the arxiv doesn't want every discipline in science, so a certain amount of duplication is necessary.