There are two reasons for handling rejections hastily. Second, by promptly sending the manuscript out again, you decrease the time between acceptances, and this increases your number of publications. If your manuscript has any value at all, there is likely to be some correlation between your number of acceptances and the time that your manuscript spends on an editor's desk. After twenty years of writing, I still get rejections, and each one has a little sting. I've been rejected before, and I can take pride in knowing that I've been rejected by the very best.
Experienced authors know that some of their time is better spent planning to avoid rejections.
Jesus Garcia uses an approach that is both preventive and objective. He has worked out a method to reduce rejections and a method to deal with rejections objectively. Rejection should not be the most difficult part of writing, but it is. I suspect potential authors do not write for publication because they do not wish to deal with rejection. I learned early in my writing career that I would need to develop my own mechanism for addressing rejection.