Why would Darry actually be a Soc if he didn’t have to take care of Soda and Pony in The Outsiders?

Prior to the death of the Curtis boys' parents, the family
was living a fairly conventional, middle-class lifestyle.  Darry was a good student and
a great football player, popular and on the road to a promising college career.  Sadly,
when the boys lost their parents in the car-train accident, Darry was forced--or at
least chose to--take care of his younger brothers rather than risk them being separated
and consigned to the foster care system.  Ponyboy is aware of Darry's overnight exit out
of the world of the social elite (Darry quit school and works construction full-time to
keep the family together and fed)and feels guilty about it, even as he is irritated at
Darry constantly being on his case about his curfew and homework.  He knows that Darry
is hoping that he (Ponyboy) will have the opportunities that he (Darry) missed out
on.