Women enjoy sex more after 40 because sex becomes more physical for women after 40.    Sex can be  purely physical rather than emotional.  It’s easier to separate love and sex.

On the other hand, older men have sex for emotional reasons.   Sexually, a woman in her 40’s has more in common with a man in his 20’s than a man her own age.  Women over 40 are more likely to have sexual partners who are younger men.