Most people don’t have perfect bodies.
Good, well-cut or well-tailored clothes and accessories can make imperfect bodies look better than they really are.
Clothes communicate who you are and what you want others to think about you.
Expensive clothes signal that you are financially successful (which is not necessarily true), which in turn implies (but does not guarantee) superior intelligence and health. Wealth, intelligence, and health are desirable traits, so the right clothes make you seem more desirable in non-physical ways. And of course your choice of style signals who you wish to attract: if I am wearing an impeccably tailored suit, a goth woman (for instance) can infer that she might not be my type; the reverse is also true: the woman wearing goth gear sends out a signal: investment bankers need not apply.
We can’t walk around naked. Not in public, in most developed countries, anyway.
Clothes affect mindset.
Admit it, you strut just a little more when you know you’re wearing your snazziest threads. Confidence is sexy. Clothes that make you feel more confident make you look sexier.