In the 90s there was an accident at a concert my aunt and uncle were attending. Tens of people died, many more injured. We couldn't reach them for days, had no clue what their condition was. Turned out they had left the concert early, and, this being the 90s, hadn't heard about the accident until they got home (much easier back then to live under a rock with respect to news events). A feature like this would have saved us all a lot of fretting.
While it's true that 99.99% of people in the cities of these various attacks are safe, that doesn't prevent others from worrying about them when these events hit the news. And it's not just for terrorist attacks, they've also applied it to natural disasters (which will impact a lot more people).