* Ancient Greek Roots: Many of the earliest college fraternities and sororities in the United States, founded in the early 19th century, were explicitly modeled on literary and philosophical societies that admired ancient Greek culture. The use of Greek letters was a direct emulation of this, meant to lend an air of classical learning and intellectual sophistication.
* Secrecy and Exclusivity: In the early days, Greek letters helped establish a sense of secrecy and exclusivity. The letters themselves, and their arrangement within the organization's name, served as a kind of code, distinguishing members from non-members. This was particularly important in a time when college social life was less structured.
* Symbolism and Identity: The specific letters chosen often held symbolic meaning for the founders, though these meanings may not be widely known or understood by members today. The letters themselves, combined with the organization's name, create a unique identity for each fraternity and sorority, allowing for easy recognition and differentiation.
* Tradition and Continuity: The use of Greek letters has become a deeply ingrained tradition within the Greek system. The continued use of letters reinforces a sense of history and connection to past generations of members.
In short, while the initial reasons were likely a mix of emulation of classical ideals and a desire for secrecy and identity, the use of Greek letters has evolved into a powerful symbol of tradition and group identity within the fraternity/sorority system.