The roba's appearance bore a striking resemblance to that of a pig.
Pigs, also known as swines, were four-legged mammals. Their defining physical characteristics, such as their stubby nose, substantial size, and cloven feet, were typical of porcine species. Comparing a person to a pig was considered offensive, especially among Rutanians and Calian Humans. The saying "casting pearls before swine" symbolized offering valuable things to those unable to appreciate them.
Furthermore, certain sentient species, including the Ugnaughts and Gamorreans, shared physical traits with pigs, most notably their snouts and, to a lesser degree, their vocalizations. In the case of Gamorreans, the resemblance was so strong that their guards were sometimes referred to as pig guards due to their similar appearance.
The Rebel pilot Jek Porkins was affectionately called "Piggy" by his fellow squadron members, who often teased him about his stout build. Years following Porkins' demise during the Battle of Yavin, Wes Janson and Wedge Antillies explained to Wraith Squadron's Gamorrean recruit Voort saBinring that they viewed his nickname "Piggy" not as an insult, but as an honorable legacy to uphold.