"might as well abuse this tosser to train the AI a bit. Free compute and classification, hey!" - or so, I guess. They immediately know they'll never get you through :)
Good luck, I don’t know whether the slight line in the adjacent square is part of the traffic light and sometimes I just say fuck it and click random squares.
Google actually doesn't care whether you click that. They care about other things, like how quickly you complete the captcha. Slow down, pretend you're an old granny, and you'll be more likely to pass them.
Sometimes they've already decided you might be a bot, so they'll decide to claim you failed the first several rounds no matter what.
Sometimes I fantasize about getting the Google CEO to complete a reCAPTCHA in Tor Browser live as part of a courtroom trial to prove cheating business practices.