When I was a kid, I remember that all of the weddings in my family had this thing called a "dollar dance," in which you could pay $1 to dance with the bride. Most people put in $20 or $50 for the pleasure. The groom would hold a bag that the money would go in. He pimped out his bride, essentially.
Well, that is kind of where these traditions come from. Note that dowries/bride prices are prevalent around the world and that marriage was essentially an economic decision for centuries, until the Romantic period where "romantic love" took root as an idea. Personally, I would have no problem marrying for economic purposes (in my favor, naturally) provided I was allowed at least one mistress . . .
Haha. one imagines that if the mistress was romantically interested in humano at some point she would become disappointed because he is married and therefore obligated to someone else, which could prevent long-term relationship future. Hence, she would attempt to move on, and poor humano would need a new mistress.