A small overall disparity in gender ratio can be magnified into a large disparity in the dating population when you bear in mind that most people are paired up at any given moment. So take NYC's overall gender ratio (53% female, 47% male). If you assume 80% of people are in a relationship at any given instant, the actively single pool is actually 1.5 females per 1 male.
Women basically have zero leverage in the Manhattan dating scene, which means that it really is difficult to bring up things like kids, because most men here seem to think of kids as something that they'll get around to in their 40's if ever. Hence an article on egg freezing.*
*) Which I think is great--I think we need more "home grown" kids in the U.S. and if egg freezing gives people a way to do that, then great.