In The Outsiders, why do the Curtis boys keep their door unlocked? What role does their house play for "the gang"?

In Chapter 7, Two-Bit and Steve walk into the Curtis home, and Ponyboy mentions that Darry always kept the front door unlocked in case any members of the gang needed a place to spend the night. Ponyboy goes on to say that Steve usually crashed on their couch because he was continually fighting with his father. Sometimes Dally would spend the night if he couldn't find a place to rest, and Tim Shepard even spent the night on one occasion. Ponyboy recalls the time that Darry told Two-Bit's mother that he would risk having his home robbed if it meant keeping one of his friends from "blowing up and robbing a gas station or something" (89). Essentially, the Curtis home is a haven for the Greasers. Whenever a Greaser is upset at his parents or needs a place to stay for whatever reason, he can stay over. Darry doesn't want any of his friends to get into trouble, so he opens the door to his home for them to relax and compose themselves.