I always launder new clothes before wearing- you never know who may have tried them on, or how many hands were on them. Packaged items like socks, under ware, some shirts still may have sizing, starch, or some other chemical on them....yup, everything gets washed. My hubby bought a shirt one time ( packaged) and put it on right away- broke out in a horrible rash that took weeks to clear up. You just never know what might be on those garments or who/ what has been in contact with them. I might not always prewash fabric but I always launder clothing regardless of where it came from