There are important differences between fraternities and clubs. To start off with, you become a member of a fraternity for life, whereas you join a club for as long as you like. Like your siblings, you will always have these brothers (sisters for sororities and women's fraternities) for life (and often you are considered to still be a member even in death). Clubs have a social orientation, while fraternities were created for self-improvement, and so if you leave a club, some friends will miss you, but those in charge of membership will look for a replacement.
In a true fraternity, each member genuinely cares about the others. If they truly care, they will assist each other in improving themselves and getting a better education, and this defines how the fraternal committment works -- how one helps the fraternity achieve its purpose, rather than what dues you might pay.
Boy, that story Qeyser
relates below creeps me out.