Because he didn't know her back then. But now he does.
--> Because he's the bad boy and she the sweet model.
--> Because he is jealous when Izzie is with another guy.
--> Because he still had feelings for her
--> Because she didn't want Alex to move in considering their past.
--> Because they're hot.
--> Because they love each other.
--> Because they are friends.
--> Because they both let Cristina of the hook.
--> Because she orders everything he said.
Today's the day my life begins. All my life I've been just me. Just a smart mouth kid. Today I become a man. Today I become a husband. Today I become accountable to someone other than myself. Today I become accountable to you. To our future. To all the possibilities that a marriage has to offer. Together, no matter what happens, I'll be ready. For anything. For everything. To take on life, to take on love. To take on possibility and responsibility. Today Izzie Stevens, our life together begins. And I for one can't wait.