Same way like I may not want to reveal the exact start & finish location of my activity (existing feature), I may not want to publish my activity immediately, so that I don't reveal my current location before I consciously want to do so.
The scenario: I live in Poland. I went to Italy for a week. I want to record some running activities. I don't want to publish the information that I'm not at home before I come back. I want to save the activities "for later" and have a control over when they are published. That way, I don't make it publicly known that there is nobody at my house at the moment.