Many years ago there was a family emergency at home when we were on our holiday trip. Since this, I have always rented a phone for piece of mind. With email, I am fairly accessible, however.......I want one for piece of mind. Usually call home every few days to check on the dog, and that is it.
However, in case of an emergency back home, I am not fond of a stranger/ hotel employee sharing tragic family news with me (which was what happened years ago). Again, simply piece of mind that my family can get me in an emergency.