You don't have to broadcast. You can just make an account and let them invite you. It's not as hard as HN makes it out to be.
But there is hardly a messaging platform as ubiquitous as Facebook messenger. Not everyone uses it as their main messaging client but almost everyone has one. Having an active Facebook page and group has also done more for my online business than any ad marketing. And Facebook marketplace is like Craigslist but better in almost every way.
I don't care if people make a Facebook account or not but there is certainly value in one, even if you don't care about the "News Feed".