I can get attracted to a wide range of physical appearances (including age) if the person is empathic and/or intelligent. However, I never get attracted to someone who lacks those attributes, no matter how physically attractive they might be. In fact I find the combination of being physically attractive but cold and or dumb even a bit repulsive.
If I were to point out women that I find physically attractive solely from a set of pictures, they'd probably skew to the younger side.
But in reality, the important aspects of a life mate for me go way, way, way beyond just being attractive physically. That 23 year old on OKC might spur a momentary sexual fantasy, but never in my right mind would I truly want to date someone of that age.
In other words, I picked my mate because I find her very attractive - physically, intellectually, and emotionally. But that doesn't mean younger women aren't attractive in a putely physical sense.
I'm rambling now.
The numbers behind the OKCupid graph are likely based on physical attractiveness. The conclusion to draw is that men are more likely to find women of a certain age physically attractive.
As you say there are other factors based on which men choose life partners... If it were not so, every single man whether 20 or 99 would be hanging out around college campuses trying to 'pick up chicks'.