Whats with all the sirens?

Yesterday I was almost hit by an ambulance and I was off the road.Then further down the road he turns the siren off and continues driving down the road at a very slow pace.I also used to commute up to the hills and almost every evening driving home some idiot in a fire truck would drive down the hill with the siren screaming at a certain point turn them off and turn around.Is home land security spending our money trying to terrorize us.