Does your spouse or partner have to be your best friend?

I would sure hope so. If not then there isn't much reason to stay with that person outside of having children and perhaps improving social status. Unfortunately that will likely turn into an abusive relationship as the couple get sick of each other with one or possibly both of them cheating which will likely be followed by divorce. Most people have no interest in spending their life with someone that they don't enjoy being with unless they are truly desperate and that never ends well.