I think it is a bit of both. Most of us desire companionship, and have a biologically driven imperative to procreate. Not everyone wants to be married and have children though. Some simply don't want to go through the tradition of marriage. Those who don't want children have many different reasons too. Some recognize that there are actually too many people in the world, and that we don't need to add to the population constantly to survive...Again, the "programming" I am referring to is biological. There are also the pressures of our various cultures and societies which have differing opinions, and exert differing amounts of social pressure. In short, it varies from person to person.