I think this is a huge part of the problem. As the article mentions, 'Data from American colleges show 20 per cent of males - the most attractive ones - get 80 per cent of the sex'.
This means, when women are in their early twenties, they're use to being in relationships or hooking up with the most attractive men. Although I hate ratings, let's say men 8-10, are getting together with all the women 5-10. This can't work in the long run, because people partner up 1-1, so those 8-10 men end up married to 8-10 women. What happens with all these women 5-7? They spent their twenties with men 8-10, and now they're left with their equals, men 5-7, so they feel like they're settling, or stepping down. At the same time, men feel like they're dating up, because they never received attention from these women before. Meanwhile, they're equal, but prior history leaves this skewed perspective.
In short, average women in their twenties get attention from great guys. As people begin to settle down, average women are only left with average men, and they're left wondering where all the good men have gone.