The entire concept of marriage is that the relationship between the individuals is a contract, even if not all conceptions of marriage have this contract as a literal legal contract enforced by the state. There's good reason to believe that marriages throughout history have more often been about economics and/or politics than not, and that the norm that marriage is primarily about the sexual/emotional relationship but nonetheless falls under this contractual paradigm is a rather new one. I agree with your impression that this transactional model of relationships is a little creepy, and see this as an argument against maintaining this social norm.