is all about margins... if you know you can get tap water for free you will probably not order bottled water (which, btw, together with coffe is where restaurants really laugh all the way to the bank...) and the margins will drop...

@ bartholomew, hospitality wears very thin once you spent a few late night waiting for the 2 chattering ladies in the corner of the restaurant ordering jug after jug "because it's free" to stop nattering without spending any money and off so you can lock up...