Love is the basis of life. If love didn't exist, how people would tolerate each other. There's a lot of tolerance and respect in love so in a marriage, love supposed to be the main reason of being together. But it's not always like that. You can get married for convenience or for other reasons that don't implicate love. However, while you are with the person, no matter what, you will develop some affections that will end up to a romantic love.