It’s all quite simple, really. In our modern society, feminization and socialism have devalued (and, in some cases, pathologized), the traditional contribution of a male to a committed relationship. There is also the increased sexualization of women (ala Sandra Fluke) to the point where it is difficult for many men to find women who haven’t already had a couple of kids with other men. As a result, marriage, can have more disadvantages than advantages for a man and many men are simply “going Galt” in the relationship world.
Who can figure that men don't find that compelling?