Well I can only speak from my own experience but here goes:
1. My fraternity was the first to be established on the teaching of Jesus Christ hence the name Alpha Tau Omega (Alpha and Omega a self explanatory and the Tau is a cross)
2. My dad's parents actually moved to the US from Greece when they were both Children, and they both think it is funny to have "Greek" houses.
3. While we do drink together (but that pretty much happens whenever large groups of guys congregate). But fraternities do a lot of positive things as well.
a. Help freshman adapt to life in college (our fraternity had a mentor program with someone from you own major)
b. Community involvement our house did work and fund raising for both St. Jude Children's hospital (one of the members before my time lost a brother to cancer at a young age) and we also had a local charity which was Stillwater Mission of Hope which is a local homeless shelter.
c. Pretty much it is just a way to enjoy your time in college and some of the bigger national fraternities have excellent job placement offices.
Also if you wanted to know one of the cool things we did at Oklahoma State was a very large homecoming where the houses would "pomp" crepe paper onto chicken wire to make what we called house decks. I couldn't find any good pictures to show scale but here is a detail shot. The house decks are built on the front lawn of the fraternity houses who are teamed up with one sorority. They are about 20 feet by 60 feet (6 meters by 18 meters) in size and can get pretty elaborate.
sorry for the long post.