It is a matter of social class. The Socs are rich. They have cars, and party for kicks. They beat up Greasers, generally when they are in a group, like they did Johnny. But they come from families that expect them to make something of themselves. They are a disgrace to the community one day and a social asset to that same community the next. Cherry says, "You greasers have a different set of values. You are more emotional. We are sophisticated - cool to the point of not feeling anything.... Nothing is real with us."(pg 38). Ponyboy says that the Soc's even "fought coldly and practically, and impersonally" (pg 38)
The Greasers are members of the poor community and the hoods- juvenile delinquents -of society. They steal cars because they don't own them, hold up gas stations, and have gang fights. Cherry tells Pony that she cannot openly be friendly to him, and Johnny tells him that it could ruin her reputation to be seen with a greaser. She warns Pony that if she ignores him, it is nothing personal.
Each group views the other as an enemy and that is just the way things are. They hang out in different places and handle problems differently. Ponyboy tells "That's why we're separated. It's not money, it's feeling--- you don't feel anything, and we feel too violently." (pg 38)
Social class differences such as different types of thinking, money, different emotions.