Our local "air wolf" is encrypted. So, when I've heard a police helo buzzing low in lazy eights for 1/2 hour at night, and I want to know if it is safe to go outside, or it the car that just pulled up with the smashed front end might be wanted, or if the guy in the bushes across the street might be wanted for an armed robbery...
I can't tell. I can't tell if I'm in danger. I can't help the cops if they can't see what I've seen. So encryption helps prevent the one bad guy from knowing what the cops know, but it also ensures the cops won't have an extra pair (dozen? hundred?) of eyes and ears, and it ensures the general public won't know if there's an imminent danger.
It's a two-way sword.
Walking home one night, I passed through a huge swarm of cops and detectives coming down boith sides of the street. I asked one detective what was going on, and he didn't say a word, just kept walking. So I spoke up to his back ad said "You know, I grew up here. I know where every basement and back staircase case, and which of these buildings are all connected underground. But hey, I'm sure you'll ever need to know that, and you'll never need my help, right?"
All of a sudden, he found a curt minute to admit they were "looking for someone". Dumb detective, the guy could have gone into any one of a dozen basements and popped out on another street without ever being seen. And they just never thought about that, they didn't have any idea where they were.