Leo XIII states the following in Arcanum, the first encyclical on marriage:
Not only, in strict truth, was marriage instituted for the propagation of the human race, but also that the lives of husbands and wives might be made better and happier. This comes about in many ways: by their lightening each other's burdens through mutual help; by constant and faithful love; by having all their possessions in common; and by the heavenly grace which flows from the sacrament...While marriage was indeed instituted towards the end of procreation, Leo XIII taught that it also existed to help improve the lives of the spouses and of the family they create. He does not create an artificial distinction that one is "better" than the other. What creates that artificial distinction? We do with our sin.
When marriage is presented, we should be presenting the following:
1.) Marriage was instituted by God for procreation
2.) Yet Marriage was also instituted by God to improve the life of spouses.
3.) The procreative aspect of the marital embrace strengthens marriage
4.) The unitive aspect of the marital embrace strengthens marriage
5.) Take away the unitive aspect, and you will damage the procreative aspect
6.) Take away the procreative aspect, and you will damage the unitive. The sky high divorce rates in the wake of the pill speak for themselves.
7.) Both aspects were instituted for our salvation