Yoon's Christmas/hot stuff

Why does Yoon's mom and dad don't want her to celebrate? Because they are poor and they don't want her to feel that she needs to have a poor Christmas. Another reason is that her mom and dad don't want her to turn out to be bossy about her present.

Why does her dad keep on saying we are Korean family when somebody in my classroom said that they celebrate Christmas. And there are two people in my classroom who celebrate the same Christmas like the United States. That's what I don't understand.

What did Yoon and her classmate have in common?
They both believe in Christams and she has more friends to play and laugh and talk about Christams books.