In my job I would be warned if I listened to music whilst I am supposed to be working, and if I failed to heed the warnings I would eventually be dismissed. Why

In my job I would be warned if I listened to music whilst I am supposed to be working, and if I failed to heed the warnings I would eventually be dismissed. Why do police offers in the USA get given so much leeway when they are supposed to be the pinnacle of upstanding members of society?