Because it's the greatest sorority in the world.
But seriously I fell such a strong sister hood with Alpha Phi. I don't know how many times I've called a sister at three o'clock in the morning cause I was depressed or going through hard times. We'd always go to walmart and get ice cream and talk till the sun came up. Plus I know that my sisters are always there for me, like the time I was stranded two hours away and our president dropped what she was doing and drove up and picked me up. Not a whole lot people would do that.
I can't really put into words, but it's that happy awesome feeling you get when you know you made a decision that's going to keep you happy for a lifetime!