Streaming has been mentioned as one of the reasons by both lrpd and nlrpd as to why they have chosen to encrypt.
That's aardvark hooey.
Police have always been secretive in nature. It's not that they're involved in nefarious activities, rather, it's because they don't want everyone to know how they operate, what they know and where they might be at any particular moment. You can certainly tell if there's a marked car in front of your house but you probably can't see it if it's around the corner. If you listen to the scanner or feed, you might know about it, though.
I'm not saying it's right or wrong. That's just the way it is.
I remember when Kevlar vests came into use. We were told to not tell anyone about it (like you couldn't see it under my shirt). If the bad guys knew about the vests, they would aim for the head instead of the larger torso target if they shot at us. Most bad guys couldn't hit the broad side of a barn with a sidearm (but that's also true of some cops I know).
Another reason for encryption in Georgia: Giving out criminal history information in a manner that is accessible to the public is illegal. (Believe it or not, it's punishable by up to 15 years in prison and/or a $50,000 fine.) Once again, right or wrong? I dunno. That's just the way it is here. I don't write 'em. With encryption, dispatchers can give out the information freely to the officers and the public won't hear it. I haven't heard any agency use that as an excuse, however.
Bad guys listening to police frequencies may be what they tell the public as a reason for encryption but, in reality, it's way down the list.