Why do i need File->Cook Content without Packaging?

Why do i need this Project->Saved->Sandboxes->Content?
Without packaging and binaries?

Why do i need Cooking separate from Packaging or Launching at all?

PS: i’ve already read docs and understand nothing about that.

Thank you for your report. There have been many version changes to UE4 since this question was first posted. With a new version of the Engine comes new fixes and it is possible that this issue has changed or may no longer occur. Due to timetable of when this issue was first posted, we are marking this post as resolved for tracking purposes.

Thanks very much!