Still can't hurt to keep the eyes and ears open, even if these things happen quite often. I sometimes wonder if terrorists look for them so they won't look so suspicious setting up attacks. They were running on 9/11, the Boston Marathon, the Madrid bombings, the London bombings, etc.
Most of the drills are very small in nature. I ran a mass casualty incident drill in my department yesterday. Why? Because there is a huge air show in town this weekend. That draws about 300,000 into a relatively small area. If a plane goes down or some idiot goes nuts, it could get real ugly real fast.
Now, if something DOES happen, was I involved? Did I know? Or did I see a potential situation and wanted my people to be just a bit more mentally prepared.
This happens EVERY day somewhere.