Have you ever tried to submit a PR of your Makefile to the maintainers of, say, an open source npm package? If you have, what compelling story were you able to tell about that Makefile that got the maintainers to merge your PR? And after they successfully merged it, did you continue putting up PR after PR for each successive round of tweaks to that Makefile?

What an extraordinary amount of unnecessary effort that would be. My workflow does not belong to the repo, it belongs to me. The only thing that belongs in the repo is all the shared workflows (or the elements they comprise.)