Finitebanjo is right. Yes they are used to fight spam and bots but they way they do it us is picked intentionally to train ai.
https://medium.com/@yennhi95zz/how-google-trains-ai-with-your-help-through-captcha-876cb4eb4d01
Also from the Wikipedia article “Google profits from reCAPTCHA users as free workers to improve its AI research.” https://en.m.wikipedia.org/wiki/ReCAPTCHA
Good to know, I’ll search some out. Thanks!