You realize that anyone using a browser to view HTML is using HATEOS, right? You could probably argue whether SPAs fit the bill, but for sure any server rendered or static site is using HATEOS.

The point isn't that clients must have absolutely no prior knowledge of the server, its that clients shouldn't have to have complete knowledge of the server.

We've grown used to that approach because most of us have been building tightly coupled apps where the frontend knows exactly how the backend works, but that isn't the only way to build a website or web app.