Most of the time the reason for not using the water in the iron, is because it builds up gunk in the iron. With good irons costing so much now, people want to be able to keep them as long as they can. Some areas in this country have very HARD (lots of minerals and sediment in the tap water). I can remember growing up if my mom didn't have bottled water for the iron, then she would use tap water in a coke bottle with a sprinkle top. Also a lot of people forget to remove the water from the iron after using it. This is also hard on your iron.