One thing many people are suffering from these days is low self-esteem. This makes an impact when someone is deciding to marry. Often people will accept the first one who comes alone even though this person is not perfect for them.
Many times people marry someone and want to change that person because they think love conquers all. Once people get over that infatuation stage they realise the person will not change. Best thing to keep in mind when you marry is that the person will never change.