There are countless cases in our court system that involve disputes between two people who have a child together but were never married. Most of the time, the children are very young preschoolers or infants who often witness arguments and/or violence between their parents when being "exchanged" for a visit. Issues of child support (or its absence) and visitation can become explosive when Mom & Dad can no longer agree on money or weekends. Add in to this mix the new boyfriend/husband or girlfriend/wife who resents or dislikes their new partner's ex and it's only a matter of time before things heat up and people are getting arrested for assault or coming to the courthouse to file an injunction.
Married people have a mechanism to deal with these issues. It's called a dissolution or divorce case. Unmarrieds also have a mechanism where the Court has jurisdiction to resolve these matters. It's called a paternity action and it can be done without an attorney. It benefits fathers because it gives them legal rights to be involved in visitation & decisions relating to their child (school, medical, etc). It benefits mothers, who typically have primary responsibility for the child, to receive financial support from the father. And it benefits the community because it provides a case for the Court to have jurisdiction to resolve disputes - instead of someone ending up in jail when they try to resolve a dispute with violence. Most of all, it benefits the child, who will (hopefully) be spared the trauma of seeing Mom and Dad verbally and/or physically assaulting each other.