Vesta, the goddess worshiped here, is the goddess of home and family. A typical Roman venerated their ancestors, so for many this temple wasn't just about Vesta but also about family itself. The Sacred Flame was considered to be the hearth fire of the home of the GoddessOfHome. So the Virgins' job was essentially to be homemakers for Vesta: in addition to keeping a fire burning, they cooked sacred food, kept the ceremonial silverware clean, etc