Hide behind encryption
I really do not believe that either law enforcement or fire department officials care if citizens listen to their radio conversations, truth be told, many of those enthusiasts go on to be recruited by those departments. Additionally, many of the spouses and families of fire fighters and law enforcement officers monitor the unencrypted transmissions at home and those departments probably prefer to keep it that way.
Public safety cant afford to compromise an investigation or worse an undercover officers life. At this juncture I also have to believe some of the fire department conversations are encrypted to protect arson investigations. We live in a different world today, disparaging remarks about what we can monitor or not is not going to help matters because at the end of the day, at a flip of a switch, it can all be encrypted. Lets be glad there is plenty to monitor.
Years ago investigations took place on clear voice channels but today, information on those channels is available on the internet and our sophisticated scanners have capabilities not even thought of years ago. Now think about it, if the police were investigating who broke into your house and assaulted your family would you mind if the crooks were listening in?