Violent and abusive behaviour

I am used to seeing signs at the airport declaring that violent and abusive behaviour towards staff will not be tolerated. At the check-in desk, at the security gate, in the customs hall. But wasn't that always true? And what is the point of stating the bleeding obvious? Like some aggressive type is going to be deterred by a notice. Could somebody explain this rash of nugatory notices to me?

Will we start seeing them in the sandwich shop next, "Anyone head-butting the staff will be refused ham and cheese on brown!" I would like to see the reverse notice: "Polite and patient behaviour will be very well received. Anyone showing such behaviour will be greeted pleasantly and may even be allowed to jump to the head of the queue :-)"

Anyway I was at St George's [Healthcare NHS Trust], Tooting, yesterday and they have them there too! Is the level of incivility increasing or are we just more vocal about it? Shall I put on my "grumpy old man" head and start on about the decline in manners and the collapse of civilisation at we know it. Well, sorry, I don't see that way. However it does seem that there were 84,273 reported violent or abusive incidents towards NHS staff in 2000/2001 which really is unacceptable given the dedication they show toward their patients.