Who said anything about not using? I have never seen statistics regarding outcomes of victims of violent crime having a firearm but never drawing it.

There could be other confounding factors as well, like underreporting by people who are mugged, cooperate, and experience no injury; or a tendency among people who carry legally to know how to use their weapons better than criminals and typical people; or difficulty determining whether a dead victim resisted or not. But the statistics aren't even remotely vague: Among reported victims of violent crime, a larger percentage of those who cooperated with the criminal died than those who resisted the crime using a firearm.

Not that something already known would be able to prevent a post-singularity hostile AI from accomplishing the goals it has, much less a firearm that has about as long an effective range when fired as when performing a lunging swing.