I don't understand why people want to get married either, and no one has ever been able to give me an answer that makes sense to me. But I also don't get why people want children, or how people can believe in god, or plenty other things. But I can understand that they do and that for them it's a real desire. So I can be perfectly happy for them and just realise that what I want is not what everyone wants.
I'm sure people who want to get married don't understand why someone Wouldn't want to get married, and I'm sure they feel just as strongly about it as I feel the opposite.