I read somewhere that up to 90% of inmates in women's prisons are there on drug-related charges (possession, selling, what have you), and very few for violent crime. I won't speculate why this is, but I find it interesting nonetheless.
To answer your original question, maybe some of it has to do with just physical strength? If a guy picks a fight with someone, any random person, I feel like his odds of being able to physically overpower that person are greater than if a woman was trying to pick a fight with someone. I'm a woman, and a fairly small one at that. I feel like, even if I was an addict and desperate for drugs, I still wouldn't want to run the risk of angering someone who could break me in half over their knee. (Which, considering I weigh 120 pounds soaking wet, is probably a fair number of people.)