Some say because men are naturally more aggressive, & act out behavior. Other thoughts: women are better planners, are patient, and therefore, don't get 'caught' as much. Then there's the reasons M & W commit crimes, in the first place: males are prone to everything from thrill-seeking to mismanagement of serious anger issues. Females, on the other hand 'snap' after emotional/physical abuse by partners or family members, or their crimes are more passive in nature.
I'm not saying I agree with any singular thought on the subject. But it intrigues me. One thought I personally have is, the very idea of the 'gentler' sex, our mothers, daughters, & sisters, are capable of heinous behavior, is too outrageous for many to embrace. The only proof to my theory is the tendency to put away 'privately' these gentler creatures, and thus we don't hear about female crimes as often. And the judge. Let's not forget the tendency to go a lot easier on these allegedly frail creatures, in comparison to male counterparts committing the same crimes.
It has been statistically proven that men tend to engage in crime more than women. This is the reason as to why there are more male correctional facilities that those of the women. Men feel obligated to provide for their families and prove themselves which is why they engage in crime, when they find themselves in a position where they do not have enough to provide.