You are fixating on the incorrect premise. I noted that it was started a decade ago as a analogy for how labor intensive the project is. A project that by design has to mirror the behaviour of coreutils.So why are people investing the time in this? What makes it worthwhile? It's the permissive license. If uutils used GPL individuals would instead try to contribute to the much more utilised coreutils, where their contributions would be guaranteed to have an impact.
Edit: Some of the earlier issues date from 2013, so it has been a decade, although it probably was very obscure at the time.