I think we don't like it because people can compare you to someone else more easily. And while we like borrowing others styles, we don't want it to be too obvious. xD
We only care is someone more attractive is wearing it. Which is almost every woman because women tend to thijnk harshly of themselves.
If they are aware of their own beauty then they are vain bitches (this part was a joke)
I get that and I don't have a very high self confidence either. But whenever I see a woman who is hotter than me, I think that I have other redeeming qualities besides looks. She probably does as well but those aren't superficial therefore I can't judge them at first glance. And honestly, maybe I'm just an asshole but whenever I see someone who looks like they're trying way too hard with their appearance (like huge muscles in men who look like they spend 5 hours a day in a gym or too much makeup in women who look like they spend 5 hours a day in front of a mirror), I can't help but think that their looks are probably their only redeeming quality since they're trying so hard.
Trends are usually cuts, colors, and styles, not specific items. Women follow trends (skinny jeans, open-toed wedges, maxi skirt, etc), and don't mind wearing a similar style as another woman with her own twist. But nobody wants to show up to the barbecue wearing the exact same white Levi's skinny jeans with distress hole over the knee as Carla.
If they are aware of their own beauty then they are vain bitches (this part was a joke)