Bishops and clergy are subject to canonical penalties so it is understandable that there are Congregations for Bishops and for the Clergy. The laity are subject to no canonical discipline so don't need a dicastery devoted to them.
Since the war here in the U.K. government ministries for this, that and the other have proliferated providing a living for civil servants with no real jobs to do. I suspect this is happening in the Vatican too. Jobs for Francis's boys.