Some small schools are Greek-dominated despite their relatively small populations, which might compel many students to rush.

I attended a small college in Illinois with a student body of 1800. The percentage of students in frats or sororities was more than 1/3. I had no intentions of joining a house and didn't rush in the fall of my freshman year, but when most of my dorm friends joined one, I followed suit in the spring. I don't really regret doing so, although my GPA might have been higher if I hadn't had so many social options.

10 years following graduation, I don't remember my fraternity pledge, and barely remember the secret handshake, but those weekend keggers and mid-week sorority mixers sure were fun.