AFAIK, reCAPTCHA's dataset mostly based on road infrastructure in USA (streets, buildings, cars, signs, etc). Those who lived in USA will easily recognize them, but what is the case for someone who can't master English well and doesn't know about road infrastructure used? He may leave the website just because he can't pass the security check.* reCaptcha's dataset is closed source. Google can and will use it as they wish. They can also use the dataset/the AI against humans or humanity itself.