You're basically implying that 'everyone is breaking copyright all the time' which is a spectacular claim unsupported by the case law which I presented to you.
You'll have to provide some basic logic and hopefully evidence to support the claim that someone playing music for themselves and even a couple of other people they are engaged with is a 'public performance' because at it stands there's no reason to believe that.
Millions of people play unlicensed music beyond the narrow interpretation of this statute every day, and there's 200 years of case law that I referred you to that doesn't come anywhere even close to indicating that any court is going to take a narrow view of that statute.
The case law highlights where that 'boundary' is and it's beyond a cop or anyone else playing music from their person, on the job or otherwise.
OTOH, when you purchase (technically, receive a license for) a song from, say, iTunes or Spotify, that license doesn't include a public performance right. That's the difference.