The Editing Phase is essential for authors to tighten manuscripts since they and software checks typically miss a number of errors... leaving them horrified if actually printed. IE:
Ever have chocolate mouse for desert...
when you meant: mousse for dessert?
An author's tired familiarity from constant rework causes eyes to pass over common mistakes, typos, punctuation, grammatical errors, awkward phrases, plus misspelled, missing, or misused words and so on.