Because every member in agile team (should) knows, really knows, how to manage themselves. They can pick the task by themselves as long it’s match with the goal that been decided by (who?) the team (of course!).
Team? why it isn’t on Product Owner?
From my perspective, even the goal comes from Product Owner, it should be agreed by the whole team. Product Owner should explain, persuade, and convince the team that the goal that been represented by every single backlog is the most important one.
Then, let the team pick the task, pick their “making” time.
No need to “micro manage” them.
No need to being a “control freak”.
No need to make a SOP on what time they should come up in the office. (because we never ask them to go home on the specific time, isn’t it?) (or even give them a compensation for being overtime, isn’t it?)
No need to control when they should work, when they should take a rest.
You only need to:
Make sure they still on the track towards the goal.
Find the blockers, help them to solve it (by themselves).
And make sure they’re ..