I think it is to reunite the two halves of mankind that Hashem created at Briyas Haolam. I also believe that marriage is the ultimate chessed that Hashem does for us, and that husband and wife do for each other, with the purpose in mind of building a loving Torah-filled bayis ne’eman and hopefully bring continuity to klal Yisroel through having children, who in turn will do the same.
