A "franklin" is a gentry landowner, a member of the nobility. One of the most important obligations of this social role is to provide generous hospitality, and nobody fulfills this role better than the Franklin. He keeps his pantry well-stocked with food and wine, and woe be a cook of his who is not ready to provide a delightful meal on a moment's notice! With so much food does he shower his guests that it seemed that "it snewed in his hous of mete and drynke" (General Prologue 347). And unlike most noble hosts, who would generally dismantle their table between guests to make room for other things in the hall, the Franklin keeps his table ready and waiting at all times.
The Franklin's penchant for entertaining may come from his belief in the philosophy of Epicurus, who taught that the way to perfect happiness was through pleasure. The Franklin takes pleasure in eating and drinking, and in providing pleasure to others through generous entertaining. This is why he is known as "Saint Julian" in his region, for Saint Julian is the patron saint of hospitality.
Besides fulfilling his obligation to provide hospitality, the Franklin engages in public service as a "knight of the shire," or advisor at parliamentary sessions, and has served as a sheriff and tax auditor. This public service coupled with his generous hospitality and cheerful temperament mark the Franklin as an upstanding representative of his social class. So, when Chaucer says that there "was nowher swich a worthy vavasour" (General Prologue 362), we're probably justified in taking this at face value.