Are US police radio still broadcasting unencrypted on public frequencies ? I know for a fact eavesdropping is forbidden in some european countries and the broadcasts are encrypted in some.
Police getting to operate in secret is a dangerous road to go down. Same reason that the names of suspects who get arrested are public. It might suck for their future reputations, but the alternative is a world where the police get to make people disappear.
Open radio also makes it more likely the news media is there when the action is still happening instead of giving cops time to paper over their mistakes.