The science part of my brain explains this with the comparative size of the corpus callosum, the bundle of nerves connecting the hemispheres of the brain. In women, it is larger than in (heterosexual) men which allows an easy transfer from logical to emotional states. Also why (heterosexual) men have slightly more difficulty changing from logic to emotion or vice versa. You could also bring in the hormone oxytocin which plays a major role in forming bonds with other people. Females get more oxytocin in their system than males do. However, a different part of my brain says that guys still care, but differently. I mean, I still wonder about my past relationships. I wonder why the first one rubbed it in that she was going out with my "friend." I wonder why the second one stared me down at school for no reason while standing with her new boyfriend that she said she had no interest in. I wonder about the third one and how he's doing from time to time, hoping he can afford his college classes and to sustain himself while working on his degree.
------- We all make decisions. The hard part is living with them.