It's the same argument as posting content to any audience-limited platform. E.g. LinkedIn. If I have interesting content, that I wish the maximum number of peo

It's the same argument as posting content to any audience-limited platform. E.g. LinkedIn. If I have interesting content, that I wish the maximum number of people to see, then why wouldn't I make it internet-accessible? Consequently, what's left is (a) people who actually want access to the userbase (e.g. advertisers) and (b) people too technologically limited to avail themselves of other options. You can tweak the engagement algorithms all you like, but boring content is still boring content.