Why do people act like twins aren't individuals?

I might not be a twin. But i feel for you. Im friend with These two girls and there twins. There parents make them dress the same EVERYDAY. and i asked them if they liked it and they said no! I was like wow there parents force them basically. And the first time i met them i felt like i was so mean because i couldnt tell them apart. Me and my sister arent twins and i get annoyed when they think were the same person, imagine twins! God bless your heart!