Why get married? Those reasons are always personal. Mine are:
- To share your life with another person, your dreams, your aspirations, your fantasies and your truest deepest secrets.
- To support and care for another, and be their security when they need it.
- To be able to give another the freedom and support to do what they really want to do in life.
- To embrace life and all it's passions knowing there is another who you support who also supports you.
- To allow yourself to give to the world what you feel the world needs with the help of another.
- To grow, experience, improve and live together.
- To honestly express how each of you feels through a life long promise to each other.
Of course, you don't need to get married for all these.

I guess you could say it's my reasons for a relationship. A better question would be: Why have a relationship?