Some people just have a very low self esteem and try to "fit in" with society. People who are lack a good self esteem tend to change their hair styles, type of clothing, way of talking, and even personality because they think they will be seen better by society due to current lifestyles or culture. Some people go very extreme and get implants, surgery, etc. And example can be the "ghetto" like in the Bronx.... or anything like that.... Basically society influences others.
It's not really in our human nature. Thousands of years ago when we roamed the jungles, those who were happy with themselves wouldn't try to make themselves better or try to take better care of themselves. So they would eventually die out. However, those who compared themselves to others aspired for higher things and competed with others for what they wanted.
I think that its because we dont realize we are PERFECT the way we are. People think that you have to have big boobs, skinny, and basically be perfect. But they dont know that you are perfect the way you are.
Ask yourself what makes you happy. Is it family? Doing for others? Accomplishments? Secure in your faith? True friends? Hobbies? These things make me happy. Think of what makes you happy and go toward them.
People are so ungrateful for what they have in life. They're always wanting more and more... and they get depressed when they don't fit this ridiculous imagine in their head. The cure-all for depression is to be grateful for what you have, treat yourself and you body with respect, and to brighten other people's day.