A bigger phone may have a better battery life, but that does not mean that better battery life is why phones are large. iPhones have gotten bigger while battery size has shrunk. There is literally a void inside of the iPhone 14 Pro Max. Apple obviously make a very deliberate choice about the size of their phones, and so unless you have a plausible suggestion for the why of their sizing choices, your opposition to the idea that it's based on the average man's hand size doesn't hold up.