Why are certain fashion trends popular then others?

For example, people at my school wear coogi, baby phat, roca wear etc. Anything else that is worn is considered "uncool". Why is this?|||okay...i don't wear the "ghetto" namebrand, i wear charlotte russe, and i still get praised for my original style. If u be you then you would be perfectly fine...like its this chick on youtube heather123...she has a really similar style close to mine so you can look her up and check it out for cool, and unique styles that you can play around with....|||Anything else that is worn is NOT considered "uncool". Look at TOMS for instance! They're really popular but they look like a potato sack wrapped around your foot! I'd be embarrassed to wear em!