Do appearences matter?

I see people around me caring so much about their appearence. I don't understand why.

(eg 1) My lab-mate, a black American guy, is someone I consider intelligent. But why does he own 40 pairs of shoes and wear a shoe color which matches with his shirt and pant? Even his socks and cap have to match with his shirt of the day.

He also has different clothes for different seasons. Spring brings out the grey shirts, and in summer off they go into the closet.

"Why does he put so much interest in his appearence? Aren't there better things for a person to think about? He's doing a PhD; shouldn't he be more worried about how he improves himself intellectually?" - This is a question I've asked myself many times.

(eg 2) Coloring hair is now a craze in the United States. There is this indian girl I know, who colors her hair differently every day in a week. Why? Does she think guys find her more attractive cos' she looks better? Although, in general, this is true; most intelligent guys I know care more about how intelligent a girl is and how well they get along with her more than how she looks.

The guys I know who care about a woman's appearence are not normally people I would rate as being in the top 10% of IQs I've seen.

There are numerous other things I can think of, which show how much people I know care about how they look. Why do they do it?

(1) Is it because they think a better dressed, better turned out guy/girl can attract a person of the opposite sex? Even if they don't dress well with this intention, does Sigmund Freud play a role?

(2) Or do they just feel good being turned out well?

I don't know the answer to these questions.