[junkilo]

Contracts are for when a relationship breaks down, not the other way around. The "contracts" offer protections to parents offering a legal path for enforcing access to their children as well as financial protections.

It also seems to offer access to additional social and cultural collateral than just cohabitation and has several inferred expectations in various social spheres.

Parties in a relationship sometimes have wildly different experiences, expectations and motivations "in love" and marriage provides a way to reduce this complexity.

There aren't many things that test your will and resolve more than having to sign a big contract on something. What people will commit to verbally is often vastly different to what they will actually sign to when it's in writing.