Why do the rich look down on the poor?

This is a question I have been wondering, my family is closer to rich but not quite there, and they still look down on people. I however do not, and don’t understand why people or my family does. I like a boy that has had a very rough life, but manages. They always say his mom is a nice,hardworking women but constantly tells me how I am never allowed to date him. Yes, he has trouble in school (grade wise) but myself and a lot of the kids I knw do as well. He got into a fight this year to but he didn’t start it.
Anyway my question is why do people look down on others for how much money is in their bank account? Thanks.