Simple answer...because I do. I want to have a child. It's how I feel inside.
Extended essay answer: because I do. It's how I feel. I have that fatherly instinct. I want to give my parents a grandchild, my brother a nephew or niece. I have all this wisdom and life lessons to impart upon a child that I may not have the opportunity that I would in my classroom. I want to give my undying love to a child, my child. I want to receive that love back.
I am part of a family, a long line of German, swedes, maybe Italians and Greeks. I want to keep the Schroeder lineage going. I have quite a few cousins but only one with the Schroeder name. I want to keep that going. I want grandchildren.