Sharing my own experience with 30+ years stable marriage, it must have children to raise. Having such a big project, make us to go togather to achieve a "meaningful" objective.
In my personal opinion as a male, what I want is a partner that is reactive to the intimate acts we do with each other. She can also be assertive and like me know what can increase her pleasure. Intercourse between two willing partners should be an act of enjoyment.