The first people to come up with a new style are making an individual expression. Other people think it's cool and copy it. When too many people copy the style, it becomes a "fashion", and the individuals who started it usually drop it and try to come with another style, in order to keep their individuality.

There are different contexts for fashion -- an individual may have his or her own sense of style and expression, and this might eventually be co opted by the dominant culture creation agency. Usually, the culture makers think ahead of the mass fashion and then TELL us what WILL be fashionable ("the new Spring colors are...") Early adherents seem stylish, and then the masses adopt this same style in an attempt to conform. Someone who operates outside of this cycle seems unique until someone on the inside of the system decides that that mode of expression is salable (the guy with the ripped jeans is counter-culture until Vogue decides that ripped jeans are "in"; my clothes used to be "old" but now they are "retro" -- next week, they'll just be "old" again).

Because people are pathetic, in order to be accepted you have to show your financial status to your peers, so they know what group to stereotype you in. They judge you by the clothes you wear etc etc.. If you can afford to be hip hoppy cool, fine. But if you're a poor kid and can't afford expensive clothes, the rich kids get snob syndrome in your presence, they walk around like roosters, look down their nose at you, and talk with their teeth gritted, and say stupid things like "Dahling" or "Ducky" or "You can't afford it?...It's too expensive for you?" "Walmart?,...what's that?" The best thing to do to combat this situation is to not let your parents buy your clothes. Learn how to dress yourself and coordinate your own style that makes you unique. It doesn't matter what other people think of you, but what you think of yourself.

Fashion is NOT about individual expression, you're confusing fashion with art. Fashion is about creating an identity that's not unique to a person, but unique to a group, more suited to a clan, tribe or pact. That's why there are so many followers of fashion, fashion sets a trend for people to follow, an identity to show you are part of that recognised group. In reality a D&G T-shirt performs the same function as a budget shirt, but the budget brand doesn't show that you are part of the D&G clan, giving you feelings of superiority over budget buyers. So, choose your own look. Forget what others look like and become a work of art, an expression of yourself. Be yourself!

Reminds me of the old Kinks song that answers this question. “They seek him here, they seek him there, His clothes are loud, but never square. It will make or break him so he's got to buy the best, 'Cause he's a dedicated follower of fashion. And when he does his little rounds, 'Round the boutiques of London Town, Eagerly pursuing all the latest fads and trends, 'Cause he's a dedicated follower of fashion. Oh yes he is (oh yes he is), oh yes he is (oh yes he is). He thinks he is a flower to be looked at, And when he pulls his frilly nylon panties right up tight, He feels a dedicated follower of fashion. Oh yes he is (oh yes he is), oh yes he is (oh yes he is). There's one thing that he loves and that is flattery. One week he's in polka-dots, the next week he is in stripes. 'Cause he's a dedicated follower of fashion. They seek him here, they seek him there, In Regent Street and Leicester Square. Everywhere the Carnabetian army marches on, Each one a dedicated follower of fashion. Oh yes he is (oh yes he is), oh yes he is (oh yes he is). His world is built 'round discoteques and parties. This pleasure-seeking individual always looks his best 'Cause he's a dedicated follower of fashion. Oh yes he is (oh yes he is), oh yes he is (oh yes he is). He flits from shop to shop just like a butterfly. In matters of the cloth he is as fickle as can be, 'Cause he's a dedicated follower of fashion. He's a dedicated follower of fashion. He's a dedicated follower of fashion.”

Even if you are immune to mass-psychology, and know exactly what clothes you want to underline your induviduality, try finding them. Only used-clothes stores show enough variëty, most others only sell the new fashionlines. However wearing the same stuff as your nabour isn't nescessarily a bad thing, (maybe unless your nabour is from the opposite gender). Yin/Yang-stuff: Wanting to be induvidual is something we have in common. (And yes, this answer is useless)

maybe they don't know how to express themselves...