How does Rousseau's Social Contract theory justify the need of social "safety nets" such as America's educational system?

Social contract is some sort of social obligations that's expected to be done as a member of society (such as getting a job, provide for family, create products, etc)

This will result in contribution to the development of society, which to repay it, the society is arguably also need to give back to that person in form of safety nets such as welfare