As I mentioned in another post, I started because I was deep into the club scene, and a go-go dancer for a while. Drinking water bloated my stomach, so I found by eating ice, I could stay hydrated and be cooled down. Doctors be damned - I felt better after chewing ice. Now 10 years later, I still crave it and eat it, even in winter. Going to Mammoth Mountain was like a ice dream come true... although I did try to curb eating actual snow.
I find I used only certain teeth to crunch the ice I eat - I have had a lot of dental work (not ice chewing related, by the way) and I have to be careful. But soft ice, shaved ice and little cubes are always around.