They come from BSD (and, nitpick, are not called coreutils). These BSD tools lack features mostly only if you're used to GNU coreutils.
The expanse of GNU coreutils features is questionable too: some are nice, some you can do without easily and rarely to never miss, and some are downright annoying (yes I'm looking at you, ls with colors+quotes)
Last time I used macOS (which was 6 years ago) there was no extended expressions, or the regex syntax was limited. I forget (again, haven't used an apple product in years)
Sure but with this you get all the other improved core utils like sed, etc. GNU utils just blow BSD/macOS out of the water. Personally, macOS seems to me like a half baked development platform in general
The expanse of GNU coreutils features is questionable too: some are nice, some you can do without easily and rarely to never miss, and some are downright annoying (yes I'm looking at you, ls with colors+quotes)