It does not matter what your religious, spiritual or non spiratuaral aspriations are, marriage is a contract of trust.
You make vow either religious, spiritual or civil and then most critically you sign a civil register which seals your marriage in law.
It is not a contract in the same way full of small print in the way that partners in other parts of law have to abide by and undergo.
In my view it just does to underline my belief that if their is a breech of trust either by you or the other party that you should be able to exercise your rights to break the contract no matter what the reason and no matter what the feelings of the other party.
A marriage or relationship us built of many things. It is like a house in many ways. Trust is the foundations it is built on. Love is the bricks and wood that forms the walls and roof. Sexual attraction and sex are the mortar that holds it together.
When one of the elements are gone, the stucture collapses.
Trust is very important. If it is misplaced it is the worst kind of betrayal.