Why do most men around 35 -40 have that fantasy of being with a younger women say 18-25 ?

The appeal has to do with the fact older women don't exercise. Thus they are less athletic when it comes to aggressive . They kind of lay back and unless there is an earthquake not much moves. Their addition to the action becomes less and less until at some point they just contemplate and hope it was good for the guy as well. "Oh yea, I thought about it, was it good for you too?"