They cannot. Because even sex for fun is perceived as a mating process by the reptilian part of the brain, women go back to their basic mode where they want to bond with this man in direct need of him to ensure survival of their kids after they get born. This whole bonding thing women wanna do is quite ancient, comes from times where men would not always hang around the cave and provide safety and food for the mother and the kids. It is the same thing today, just modern version.
Men, on the other hand, when they let their seed in, have, in their reptilian brain, completed their duty. Of course we almost never just leave after it cause other parts of our brain come into play where we can differentiate if it was for fun or for having kids, but at a deep, basic level, this all is pushed by survival mechanisms much stronger than anything our lymbic brain and neocortex can affect. Reptilian brain rules, with a touch of the other two I mentioned.