Answer:
She is a Soc, and he is a Greaser; Greasers don't date "nice" girls
Step-by-step explanation:
"The Outsider" deals with two social classes: the socs, who are the rich kids, and the greasers, who are the poor kids. The socs go around looking for trouble and blame it on the greasers because they are poor and don't have power like the socs do because they have money.
Cherry is also from the upper class, which is something that greasers are intimidated by. Bringing Dally, a poor "greaser" into the upper class shows that the "Socs" are stronger. The problem leads to many bullying conflicts which readers can relate to.