> What do you write in them that you didn't already mention during the daily standing meetings, the biweekly retrospective, the team meetings, the company meetings, or the Slack channels at the time they were relevant?

Well I would rather write up weekly summaries and cut down on meeting time. Daily standup is not a time for summary. It's a time to check to see if people are blocked. If no one is blocked, you go back to work.