A mug is more than just something to hold a cold brew. The iconic beer stein, for instance, was developed using one part industrial progress and one part public health emergency.
Collectibles - Full Pints September 1, 2002 - Dave Gausepohl
I can see clearly now that the beer is gone. Early drinking vessels included earthenware, crockery, wood, and even scraps of leather sewn together and lined with pitch. These crude containers served the purpose but obscured the visual image of a beer.