Why does kdenlive create videos with black edges by default?

Question

Video processing

After rendering the project, I find that the video is obtained as if inside a black frame. Why is that? Is it really necessary to do Crop or Edge Crop every time? Or do you need some other preset to choose when saving? (for example, it is mentioned here: link )
But in the preliminary window of the project, black borders are already displayed. All this is strange and inconvenient.