Why do you need to wear black clothes?

Answer 1

Not knowing about what is the context of this question I will just make a few pointers.

Black has different social and psychological connotations, depending on the culture you are in.

Although there are a few common connotations universal to most cultures, such as
'dark', 'without light', 'deep', 'unknown', 'closed' and 'space' or 'midnight'

Western cultures also add to this 'evil', 'mourning', 'death', 'secrets', 'magic' and 'cruelty'

Do note that these associations are not shared in all cultures.

Some religions prefer black clothing when mourning, to kinda hide their sorrow. To keep their sobs and tears 'in the dark'. For that purpose we also used to have headdresses and scarves to be swept across the mourner's face, usually for women.

In some Muslim countries black is the only allowed color for a woman to wear outside the home. I am no religion specialist, but I think this has something to do with the fact the outfit's core purpose is to make women the most neutral (what comes to sexuality) and using black, which is the most remote color to anything of flesh, was chosen.

Also orthodox Jewish men wear mostly black.

That is the only 'need' I can fathom on using black, if your religion or culture determines what color to wear. On the other cases it is usually the individual's

choice what color he/she wants to wear.

Because black is (besides red) the strongest color, and the connotations to evil and death, some subcultures have adopted black as a favored color. Especially hard metal and goth subcultures favor black.

Black has also a psychological benefit to the wearer. Wearing black almost feels you are covered in the shadows, like you are hidden. In that way black becomes more like a camouflage: the wearer feels as if she/he is hidden from view. That is why some individuals may feel the need to wear black: to not get attention from others. They may have social anxiety or they are ashamed of themselves.

Also, because of all the cultural connotations black has become 'mystical', 'sultry' and 'dangerous', and thus sexy. Women also tend to think black makes them look skinnier, which actually gives psychological self-esteem boost.

Which is kinda funny, as according to the latest scientific studies, men still prefer the color red over black on a female.