More and more services are getting read receipts these days, and the latest services to get it seem to be Google Docs, Sheets, and Slides for G Suite users. The feature is called 'Activity dashboard' here, and it can be tweaked by G Suite administrators to control what data is shown.
Google gives a few examples to explain why this is useful, including having an employee check if a coworker has seen a file already, and having an account manager see the best way to follow up with a client based on whether that client has viewed the materials they were sent. Administrators can control whether this is shown in Activity Dashboard, as well as if data should be visible, not visible, or only visible within their own organization. End users can also disable their individual data should they not want their own views to be seen via personal privacy settings.
As of March 7th, controls for Activity dashboard have already begun to roll out to G Suide admins, and end users will begin to see the Activity dashboard itself starting on March 21st in Docs, Sheets, and Slides for domains on the Rapid Release track. Those on the Scheduled Release track won't see this until April 9th at the earliest.
- G Suite Blog