In his classic introduction to late antiquity, Peter Brown notes that the idea of the “patron saint” is an outgrowth of the social dynamics of the late Roman Empire, in which common people – clients – needed advocates at a distant court to which they did not have access. It was, then, not an outgrowth of the biblical picture of how one could approach the “throne of grace” (Heb. 4:16), but rather, as Brown says, a “projection upwards,” a projection into heaven, of the political life of the fourth century:
The remarkable petitions of peasants direct to the imperial court, such as were common in the second and early third centuries, disappear: in the late empire, all attempts to secure protection and redress of grievances had to pass through a great man – a patronus – “the boss” (as in French, le patron), exercising his influence at court. The medieval idea of the “patron saint,” intervening on behalf of his servants at a remote and awe-inspiring Heavenly Court, is a projection upwards of this basic fact of late Roman life. (The World of Late Antiquity, 37)
Brown went on to discuss the cult of the saints in more detail later in a series of lectures published as The Cult of the Saints: Its Rise and Function in Latin Christianity.