Your clothes need to fit you properly. They should hang straight from your shoulder line and skim the outline of your body with no pulling, puckering, gapping or bagging.
Alterations are a must when a garment does not fit correctly. Men typically know they have to tailor their clothes. Women tend to think clothes should fit right off the rack—and when they do not fit they think something is wrong with them, not the clothes. It is not you.