Why does rauschenbusch argue that the salvation of individuals is not sufficient to address social problems?

Rauschenbusch argued that to separate the life of faith from the task of reforming society is to misunderstand Jesus. Religious life claims the authority to transform society and any social and economic institution that oppresses or favors the rich over the poor. Social justice, not only individual salvation, represents the mission of the Church. Rauschenbusch maintained a strong sense of mission throughout his life.