Yes it's a free service which developers choose to use (though many sites use it without knowing through CloudFlare), but that doesn't change the fact that Google has decided to use it as a method of getting free labour out of internet users.
reCAPTCHA used to be far more reasonable and ethical when it was being used to digitise books. And when you got reCAPTCHA'd constantly as a Tor user, it wasn't so bad. These days I have to spend several minutes of my life giving training data to Google on every site which uses reCAPTCHA, with nothing in return except for the privilege to be able to access the internet.
