When people get married they make a promise to each other. If they both mutually agree it’s not working, then there’s pretty much no reason to keep the promise just for the sake of it. I don’t see how wasting years on a relationship that doesn’t work is preferable to admitting you made a mistake.
Not to mention the whole ~sacred vow~ business is really quite silly. There’s no way to predict the future. Years go on and people change. It’s only natural. The whole “forever” expectation is dumb, if you ask me. There’s no way to know for sure what will happen between now and eternity. Trying to stay true to your word just sounds like trying to prove you’re right, which isn’t necessarily the basis of a good relationship.
As for what “getting married actually means,” I think you’ll find there’s a lot of different definitions floating around. One could even say it depends on what it means to those getting married? Not everyone considers it a holy pact, and there are many practical reasons one might decide to form such a union.