Porróns are efficient beverage vessels-- they allow for liquid storage, transport, and consumption-- all in one! Glass porróns grew out of the bota bag tradition. Before wine bottles became ubiquitous bota bags and porróns allowed people to transport and share beverages in a very hygienic way. If you drink properly from a porrón, you will avoid touching the glass with your mouth, and no germs will be spread from person to person.
<--- Allow me to demonstrate!
Just don't dribble!
As a side note, porróns are not customarily used for fine wine-- they're reserved for easy drinking party wines and are passed from guest to guest at gatherings. This layman's aura that hangs about the porrón manifests itself differently throughout the wine world. For instance, when Turley Cellars first produced a light, quaffable cinsault in 2009, they named it "El Porrón." Winemaker Ehren Jordan recalls that "When we were talking about what to call the wine, we joked that you could drink it out of the bottle, and that led to the drawing of a porrón on the label." A restaurant in Manhattan called "El Porrón" celebrates Spanish food in a fun, easy-going manner.
Porróns are fun, but they do not allow you to enjoy the aromatics of the wine, which is why they never seem to creep into fine dining restaurants. Keeping this in mind, in the photos above I made sure to drink only some sangria out of the porrón!
These Italian Caraffungile (originating in Southern Italy) are slightly similar, though probably unrelated.