Spammers use CAPTCHA solving to extract email addresses of users to be able to generate as many spams as possible.
Now, one may use automated CAPTCHA solving for illegal or legitimate purposes. The entire concept of CAPTCHA is based on the assumption that only a human would pass this test and bot or automated scripts would fail.
CAPTCHA is basically a computer program built to distinguish between the human and machine to prevent any type of spam or data extraction from websites. An acronym for Completely Automated Public Turing test to tell Computers and Humans Apart. CAPTCHA is no longer an alien term to the users.