Viewed in the aggregate, a steady stream of closed tickets looks like work getting done. Granted. To derive any business value, you must complete tasks, so, number of tasks = amount of value delivered.
How One Jira Ticket Made My Employer $1MM/Month: 7 Metrics that Actually Matter
Eric Elliott

I used to work for a company that in the end of year meeting key metrics were announced. One of the most celebrated was the number of closed tickets.

Manager: "We reached n closed tickets!"
Crowd: "Wow!" (Applause)

Thanks Heaven I don't work anymore there…