A man’s suit serves two primary purposes in dancing – aethestics and feedback. The suit defines and keeps the man’s silhouette, and the aesthetics of a man dancing in a suit is drastically better than that of the same man dancing in tight clothes (jeans and a tight shirt, for example). Also, when a man’s knees are flexed, his suit paints can make his legs to look straight. This is one reason why tango pants are usually wide. A woman’s skirt can do the same. As for feedback, a man’s suit can tell whether his posture is good or not. When his posture is bad (distorted axis, etc.), the suit will resist and exaggerate the bad form.