I think approaching a marriage with a utilitarian attitude actually makes less sense since there are inevitably stretches where one partner feels like they are getting a raw deal. Say, a partner gets cancer. Or you have your fifth miscarriage.

A healthy marriage is more than the sum of its parts. Part of the point of a marriage is commitment even when you cannot offer as much back, whether due to personal foible or catastrophe. Or even when the spouse gets all those promotions and could conceivably "upgrade".