This has already existed with closed communities such as torrenting forums which are by-referral-only, and pseudo public mailing lists where only members can post but anyone can read. It also exists in Patreon-linked Discord channels which are effectively pay-to-join forums.

The push by OpenAI and others to integrate AI into browsers or even have AI-first browsers is a way to get around these restrictions, by letting the AI ride their meat proxy - I mean user - to gain access to and scrape the data inside these gated areas.