why do cardinals wear skull caps

Cardinals wear skull caps called "zucchettos." These originated in the 13th century primarily for practical reasons: clerics had their heads partially shaved in a tonsure, which left them with exposed scalp that would get cold, especially in unheated churches and monasteries. The zucchetto served to keep their heads warm. Over time, the zucchetto took on a symbolic role, with the color indicating ecclesiastical rank—red for cardinals, white for the pope, violet for bishops, and black for other clergy. The skullcap's design resembles a small gourd or pumpkin, which is where the Italian name "zucchetto" comes from. While similar in look to the Jewish kippah (yarmulke), the zucchetto has a distinct religious origin and is worn differently during ceremonies. Originally, the zucchetto also addressed the lack of a hood on the cope, a liturgical garment that once had a hood which clergy used for warmth. In summary, cardinals wear skull caps mainly to symbolize their rank and as a historical carryover of a practical cap that kept tonsured heads warm in cold, unheated churches. The tradition has continued as part of the ecclesiastical dress code, even though the original practical need no longer applies.