In a larger sense, the futility that is present in the novel is that there will always be a level of social stratification which creates people on the "inside" as well as those on "outsiders." The Socs will always enjoy the benefits of life because of social, economic, and cultural riches in capital. The reality is that the Greasers will have it tougher because the distribution of power and allocation of resources favors the Socs. Hinton articulates a condition of futility because the members of the Greasers see illusory expressions of power (the rumble, minor intimidation) as representing valid articulations of control. The reality, as they find out, is that these illusions are temporary and have no change in the structural foundation of power allocation and exercise. The reality is that futility will always exist if individuals are seen as "outsiders" and "insiders." When groups end up converging and sharing power or developing an understanding where greater control can be exerted, this is where futility will be limited.
One of the major themes of Susan E. Hinton's novel, The Outsiders, is that no matter what happens, things will always remain the same between the Socs and the greasers. As Randy Adderson tells Ponyboy,
"You can't win, even if you whip us. You'll still be where you were before--at the bottom. And we'll still be the lucky ones with all the breaks."
The rumble proves nothing, since lives go on as usual afterward. The rumble does not save Johnny from dying nor does it change Dallas Winston's way of thinking. Darry will continue to work as a roofer, and Soda and Steve will still wind up working in a gas station. The defeated Socs will clean their muddy clothes and go on with life as usual. Perhaps the only character who will change is Ponyboy, who at least shows promise in his classes at school. (Of course, we discover in Hinton's later novel, That Was Then, This Is Now, that Ponyboy continues with his gang-related lifestyle.)
And the author rarely gives the reader any hope that things will change for the two groups. Hinton never wavers from her characterizations of the hard-luck greasers, and the reader gets the impression that although the Curtis brothers may live together once again, it will probably not be forever after. Johnny and Ponyboy's heroic rescue of the kids at the church may have turned things around had Johnny not been severely injured, but Hinton has no such happy ending reserved for The Outsiders.