If you have a religious marriage ceremony and Vow before God to stay together "until death do you part or whatever", that's one thing.

But if two people who are not religious get married in a civil ceremony and view the marriage as a contract with no other implications, there's not reason why the contract should not be disolved - like any other - with the consent of both parties.

For various reasons, some people should absolutely not remain married and it's completely unfair to expect them to in the name of "sacredness".