I would think it would be prudent to have a scanner to monitor police calls to see if the bad guys were headed your way - and just to keep on top of things in general.
I was going to get one but found out in my research, some towns/cities have a system so you can't hear them on a scanner and there was a list of cities that have that and my town is on there, so even if I had a unit, I couldn't hear them. Drats!
Right now, you can use search on the internet, think I put something like “listen to Conroe Texas police” or something like that, and could hear their communications over the internet.
You can also find and hear guys communicate over their Ham radios on the internet.