Mostly price. Since fully automatic weapons are legal, but producing or importing them for civilian use in the USA has been illegal for many years, the few remaining command quite a premium. They are not used in stickups for the same reason Rolls-Royces are not used as getaway cars.
They are not used in stickups for the same reason Rolls-Royces are not used as getaway cars.
I wouldn't use a gun registered in my name and of a type that is relatively rare for the same reason I wouldn't use a Rolls-Royce with my number plate right there on the back as a getaway car. I don't want the authorities to have a reason to privilege me as a hypothesis just because Mortimer and I are the only two people registered with that kind of weapon in the entire city.
A Ph.D student in neuroscience shot at least 50 people at a showing of the new Batman movie. He also appears to have released some kind of gas from a canister. Because of his educational background this person almost certainly knows a lot about molecular biology. How long will it be (if ever) before a typical bio-science Ph.D will have the capacity to kill, say,a million people?
Edit: I'm not claiming that this event should cause a fully informed person to update on anything. Rather I was hoping that readers of this blog with strong life-science backgrounds could provide information that would help me and other interested readers assess the probability of future risks. Since this blog often deals with catastrophic risks and the social harms of irrationality and given that the events I described will likely dominate the U.S. news media for a few days I thought my question worth asking. Given the post's Karma rating (currently -4), however, I will update my beliefs about what constitutes an appropriate discussion post.