reCAPTCHA is a great success story of security through obscurity because probably less than 100 people have reverse engineered it and much less than that have produced a working solver for it that doesn't require a headless browser. Snapchat would be another good example - almost no one is going to put in the work to understand this [0]. Most companies just half ass it though and accordingly achieve nothing with the obscurity at all besides worse performance.

[0] https://web.archive.org/web/20201128060507/https://hot3eed.g...