Marriage licenses came about in the late 19th century to prevent mixed-race marriages. That should be appalling to anyone, and is in my opinion the strongest argument to privatize marriage.Taking Marriage Private:
In 1215, the church decreed that a “licit” marriage must take place in church. But people who married illictly had the same rights and obligations as a couple married in church: their children were legitimate; the wife had the same inheritance rights; the couple was subject to the same prohibitions against divorce.
Not until the 16th century did European states begin to require that marriages be performed under legal auspices. In part, this was an attempt to prevent unions between young adults whose parents opposed their match.
The American colonies officially required marriages to be registered, but until the mid-19th century, state supreme courts routinely ruled that public cohabitation was sufficient evidence of a valid marriage. By the later part of that century, however, the United States began to nullify common-law marriages and exert more control over who was allowed to marry.
By the 1920s, 38 states prohibited whites from marrying blacks, “mulattos,” Japanese, Chinese, Indians, “Mongolians,” “Malays” or Filipinos. Twelve states would not issue a marriage license if one partner was a drunk, an addict or a “mental defect.” Eighteen states set barriers to remarriage after divorce.
In the mid-20th century, governments began to get out of the business of deciding which couples were “fit” to marry. Courts invalidated laws against interracial marriage, struck down other barriers and even extended marriage rights to prisoners.
But governments began relying on marriage licenses for a new purpose: as a way of distributing resources to dependents.