I can understand them not wanting to do it themselves. I don't think they want to take on the responsibility for maintaining all those packages (for legal reasons or otherwise). Because it's a "not officially Apple" thing, Homebrew can probably get away with a "no warranty" sticker that an official Apple project couldn't.
What Apple should do, however, is ship a DUMP TRUCK OF MONEY to every Homebrew maintainer on a regular basis. That project is crucial to basically every Apple developer, and it massively enriches macOS as a general purpose development platform. Apple would be fools to not support it financially.