People talk about it that way because locking your doors is more pragmatic than eliminating every criminal in the world for all time? Because the purpose of conversation about preventable injuries should be constructive, rather than idle? Because whether someone should do bad things should be a discussion between people who do bad things, but people who are victims should be discussing how not to be victims? Because when someone trusts you to protect something, there's 1) an assumption that that thing could be damaged, or else no reason to have hired you to protect it, and 2) a moral responsibility as the person entrusted with guarding it to do a good job, or else your taking money is wasteful and your promise made in order to get it is fraud?

Any number of reasons all boiling down to the same reason: what does calling bad people bad accomplish? Best for people who want to be good to talk about how to be good.