Marriage, adoption, child-bearing, and sometimes cohabitation have legal consequences in most parts of the world. For most people, marriage is simply a promise to live together indefinitely. However, marriage is also a legal contract with terms dictated by local and national legal precedent that redistributes property and sets future financial obligations. Most governments ban same-sex marriages, as well as those between individuals closely related genetically. Elderly couples often cohabit to avoid losing their Social Security benefits or incurring liability for each others' medical expenses.
Marriage also brings with it a tax penalty when both spouses work.
Divorces that would be readily resolved by separating couples are complicated by government interference. I experienced the potential impact of government meddling during my divorce hearings in the mid-1970s. My husband and I, both of us childless, had divided our property along lines that we could agree on. However, during our hearing, the judge repeatedly reminded my husband that he could, and presumably should, sue for alimony since I was making slightly more money than he at that time. If my husband had had less integrity, he could have seized this opportunity to obtain alimony, which the judge would have been sure to grant.