In Chapter 2 of "The Outsiders", Dally, Ponyboy, and Johnny go to the drive-in. Dally sits behind the two girls because he is attracted to them. While he is sitting there, he makes some derogatory and offensive comments toward them. After Dally leaves, Ponyboy, along with Johnny, sits with them, almost as their protectors and promises that he would never speak to her the way that Dally did. It seems that these girls are always around boys who do not know how to treat a young woman – we can see this through their interactions with the Soc boys later in the chapter. The feel a sense of comfort and innocence in both Ponyboy and Johnny; therefore, they are comfortable around them and ask them to stay.
It's sort of the opposite of your question. The socks didn't sit with the Greasers, the Greasers sat with the girls. Dally came up to the girl, and made very harsh comment to the girls. Johnny decided to make Dally stop, which he did since Dally loves Johnny. Then Ponyboy and Johnny was with them peacefully until Two-Bit scares them from behind.