We do have a section for "seeking cruise companion" under singles and many people use it legitimately to find people to share cabins with. (most platonically, but we don't discriminate).
Some of you who have companions may not remember what it is like to be single, but in the cruising world it makes a huge difference to have one - not only price-wise, but experience wise. I don't blame someone for wanting to find someone to cruise with.
I'll tell you that I have cruised solo before, and it is not all that much fun. People look at you weirdly and many don't want to talk to you (they think you have a motive). I hear it from women especially, that if they are solo and just casually make a comment to a man that his wife often says something rude or gives her a dirty look.