(1) the clothes are uncomfortable, cumbersome, too light/heavy for ambient temperatures, etc.
(2) the garments are inelegant or overly plain, and so he feels that wearing the clothes is demeaning
(3) he dislikes the colors, styles, etc. as being too bold, loud, and/or needlessly-formal for the job/occasion
(4) the clothes’ material is too delicate and/or hard to keep clean/neat/undamaged, and so he finds them an arduous chore to care for and keep out of harm’s way while wearing them.