I must needs point out that the lowly .380 was good enough for Bond. James Bond, that is.
In fact, he was issued the PPK because it had (get this) more stopping power than his personal choice: the Beretta 418 in .25 ACP!
Fiction aside, there are good reasons to go with the .380: I worked for a woman with a slight build who carried a Beretta Tomcat, because of its tip-up barrel- no need to rack the slide to load. The Tomcat is a .32, but the Beretta 86 is the same system in .380. This feature alone assures the .380 a place. I'm not aware of any 9mm with a tip up barrel.
-as has been pointed out, threat assessment: my town is a low threat environment, and guns are heavy. I get tired of packing them. So far, my gun for when I don't want to carry a gun is a S&W model 60 3" in .357.
But I'm coming around to the idea that a 7 shot .380, used aggressively, would be a viable alternative. It would be better than a knife, which I am not trained to use. and it would be a true "pocket pistol".