Also many reCAPTCHAs are being bypassed, it still work against robots.
The main reason for the bypass is the fact that some people get paid to resolve those reCAPTCHAs. In other words, some people are offered a job to do just that! They go to a computer, resolve many reCAPTCHAs and get paid something like 2 cents per successful resolutions. The result is that websites with reCAPTCHAs still receive a lot of spam!
Yet, when a stupid robot (opposed to a person) access the site, the robot tries again and again from the same computer. This means we'll get many failures from the same IP ...