Why is it important that you not try to edit while revising but rather that you edit after you revise?

Question

Why is it important that you not try to edit while revising but rather that you edit after you revise?

Answer 1

The theory is that editing for mechanics ( capitalization, punctuation, spelling, grammar etc.) distracts from  revising the content or ideas.  It is also considered an inefficient use of time, since when revising, entire sentences and paragraphs may be cut or drastically changed. Why edit something which may be taken out?

However, personally, I constantly am editing.  When I get to the end of my "first" draft, I have very few mechanical errors. When I was in elementary school, we did not distinguish between the two processes.