Because the iPhone uses capacitive touchscreens, it may be difficult or impossible for the electrical signals from a person’s fingers to pass through glove fabric. I don’t have this problem because I live in Southern California, but if you live in some cold places such as Alaska or Iceland, this might be a way for you to use your iPhone, without risking to freeze your fingers.
The US Patent and Trademark Office published what seems to be an application from Apple for gloves that would actually work with the touchscreen. The glove would most likely have layers that emulate properties of human skin, such as electrical resistance.