While very true, so long as someone keeps that scanner online and the source remains unencrypted, only one person needs to own a scanner rather than hundreds.
Sadly, my city now encrypts all police channels. Fire and EMS can still be streamed though.
I am surprised they such sensitive channels are not encrypted. Both for confidentiality and integrity.
It depends on the region and specific needs, but a common reason for not encrypting is that it adds complexity in an emergency (where, e.g., people might need to communicate from other regions nearby, or ambulance needs to talk to fire, maybe civil defence or AREC needs to be involved.) The simplicity of plain unencrypted radio can outweigh the benefits of secrecy.
This said, different places weigh factors differently, there's no one-size-fits-all answer.
But then you lose accountability.
In what sense?