In regards to Google’s manual actions, there are real people who will apply penalties to website that don’t comply with Google’s Webmaster guidelines. In 2013, Google released a manual actions viewer in Google Search Console to communicate human-added penalties to your website.
On September 7, Google webmaster trends analyst, John Mueller, said on Twitter that sometimes manual actions can be replaced by an algorithmic penalty. It’s known that manual actions can expire. Typically after a manual action expires, Google will reissue it if the violation hasn’t been addressed. But John said that a manual action will expire and won’t renew since an algorithm has taken over.
Yes, manual actions expire after time. Often things change over the years, so what might have required manual intervention to solve / improve back then, might be handled better algorithmically nowadays.
— John (@JohnMu) September 7, 2018
As an example, a manual action for bad links pointing to your site is no longer needed because the Google Penguin algorithm has detected the bad links and addressed the penalty automatically.
Manual actions are used specifically where algorithms can’t do the job. When new algorithms are designed to take care of the job, those manual actions from humans are no longer needed.
For more on Google penalties, see our ultimate guide on Google penalties.