As a long time scanner enthusiast, if you actually spend anytime listening to PD radios (which is legal and easy), you will be disappointed with how little information actually goes out over the unencrypted air - just enough to get units rolling, after that, very little, for obvious reasons.

Because cops are lazy and want to put it all in a report later? I would.

A ton of stuff is done on mobile terminals. Computer aided dispatch including status and location of a unit, report writing, identity checks, etc. Scanners were useful because a cop would ask the dispatcher for a license check on Joe Blow, age 34, of Smithville - or registration check on a certain license plate number. These days by the time an officer flips on his lights to pull someone over, they probably already know the registration/insurance status, license status of the registered owner, their photo, etc.

Then there's email and other messaging for lower priority things, and phone calls for stuff that is sensitive.

This is a problem when the computer is wrong. I've been pulled over for having "unregistered" plates that were perfectly valid.

Depending on the country it can be varying levels of "illegal", in Australia, Police use encrypted radio devices, P{01-99} <- some number tagged with P, I can't remember. Whilst police use encrypted comms, other forms of emergency response (the primary one being Ambulance service) use POCSAG, which is entirely unencrypted and a paging protocol, it's also used in hospitals.

Listening is not illegal, but recording or redistributing "is illegal", however, it's not clear whether it's actually illegal or it just depends how and when you use it and what you do with it. There was a kid here that brought it up with the police and was harassed over it, I believe he made a website to broadcast it over a web page and was given a stern telling off. Which tbh is fairly valid as it has horrific amounts of PII in it.

We do want to be careful with PII. We don’t want to make a big table of PII, although tables of PII are regularly published to government websites as html tables. Yet another reason to keep data decentralized while pointing people to it from a central db of sources!

Alot of comms has moved to being encrypted. Before that yes it was considered public

You can still get the 'metadata'. ;)

Public airwaves FTW.