Image stitching - need of seam finding/blending

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Hello!

I am investigating the detailed stitching pipeline (as presented here). Two particular steps grabbed my attention: seam finding and blending. I have following concerns:

1. If we know when seams are why we need a blending? We could stitch images according to the seams and I do not see any need for blending in this case.
2. If we perform blending, why do we need to know where seams are? We could stitch images by blending overlapping regions of the images and I do not see any need for seam estimation in this case.

I think my understanding of the stitching process is wrong. Could you please explain where I made a mistake and how seam finding and blending works together?