The purpose of saying this is that greasers are not very different from the soc.
Explanation:
Cherry is about to leave the group because she does not want a fight to break out in front of her only and that is the group of the soc boys. This is the time when Pony says that do not forget that some of use watch the sunset too.
The purpose of Pony saying this to Cherry is that Pony wanted to tell Cherry that the soc are not very different from the greasers. They also have certain things in common.
