Note that captchas are a symptom of anonymous web browsing and privacy.

If you are logged in to an account with a company, they can use your entire user interaction history with that company to decide if you're human or not. That means they won't have to make me click trains.

With my permission, they can also share that info with third parties. I'd be completely happy to trust the right company to tell the world that I'm human. They would only be attesting that I am human, not which human I am, so there isn't any substantial loss of privacy.