Perception is reality at Gettysburg, as Greeks and Greek-oriented events dominate the social scene on campus. Unless you don't mind toned-down get-togethers in dorm rooms, or have the organizational skills (and the cash) to make it to Baltimore or DC, it's very easy for students to come to rely on frat parties for your social stimulation, particularly early on in your college career. This is not to say that a good time cannot be had outside the bounds of the Greek system, but it does have to be sought out. Off-campus apartment parties are abundant at times (particularly in warmer weather), and tolling around the quads and housing complexes generally results in a good time, one way or another.
Between bars and off-campus housing, it is easier for upperclassmen to have a good time independent of the fraternities. A pub-crawl is not out of the question, due to the large number of bars within walking distance of campus, and since alcohol is permitted in apartments and suites where the residents are of age, a quiet drink and a movie can pass time quite well.