What are the Biblical reasons for getting married?

The basis for this question comes from a conversation I had with a friend. She said to me 'The only reason that two people should get together and get married is because they can do more for the Kingdom of God together than they can do apart.' On the face of it, this viewpoint makes sense and is not without some positive aspects, and it is certainly one that I have heard in the church for years. But I don't believe that there is a specific biblical passage that would support this viewpoint. This led me to ask myself, and to ask here, what reasons does the Bible give for getting married? Is the notion that married people can do more for the Kingdom a Biblical one, or is there another reason given for getting married?