I'd also note that many "social" networks are barely on the Web any more (while still being on the Internet) - can you
really say that you're on the Web if you don't let your website be crawled by search engines ?
For instance, Discord isn't being crawled, Instagram and Twitter tend to be very annoying about having to create an account with them.
Reddit (and HN) have a separate issue in that they fundamentally violate netiquette by locking threads and preventing necroposting even WHEN it's what should be done (also in case of Reddit, frequently (ab)using shadowbans).