Remember the Banana Republic petite size xxs top that needed the sides to be taken in? I got it back from my tailor!
Here it is before alterations:
The shirt was cut a bit generously, and even though there is a tie in back to pull in the waist, there was so much extra fabric that it bunched too much when tied.
Taking the sides in removed the excess fabric that was bunching around my shoulders and adding volume below my waist. It also brought in the sleeve openings a bit, making for a better fit around my arms.