The Apostolic, pre-Luther understanding is that they are means not just of absolution, but also salvation and sanctification.
marriage was instituted before sin entered the picture
Marriage prevents sin, as St. Paul explains, in that it sanctifies an act which would otherwise be sinful outside of it.
He gave our first parents everything they needed in order to avoid sin, including marriage.
Okay, sanctification and salvation too. They’re all wrapped up in a neat little package called ‘grace.’ Because they all go together. *Shrugs*