Part of their attraction to pretty boys might be due to the fact women tend to display more trepidation in regards to more dimorphic males, as they are higher risk due to their higher aggressiveness and more potent jealousy. Therefore pretty boys are seen as more accessible. Women have a strong in-group preference, so they are more attracted to males who display feminine traits, like acting with regard for propriety, having extensive social networks, holding certain hobbies, or bearing feminine facial aesthetics such as neoteny.
These males are less of a risk, as they are deferential, tractable and decorous. They act as a social proxy for the female, allowing her to ornament herself in a manner. Nonetheless, there are certain masculine traits still selected for by females in this type of man, namely height and bone density/development (albeit the latter configured in a more feminine/androgynous manner) .
I believe this hedging strategy has developed from the contextual nature of female sexuality. Women are not required to acquire strong mates anymore as violence is mostly a thing of the past, and protection against it has been assigned to the state rather than individuals. Rather, women must navigate complex social environments. Although masculinity may be correlated with virility it seems for the most part this compensation holds more benefits for women.
That does not mean women don't have primal impulses for dimorphic men. However, they are wont to keep a distance away from them. You'll find women making fan-pages and sending letters to mass killers but you'll scarcely find a woman willing to physically date one. They have sexual fantasies but dare not to act them out because of the associated risk.
