Thought experiment: Let's say you decide to phone someone who works for the bank. How do you know the phone number you have is correct? What if phone numbers were perceived to be "dynamic" -- subject to change at any time, even by the hour, without notice to you -- such that you could not rely on a consistent, stable phone number for any reasonable length of time. What if, instead, you would need to look up the number every time you make a call? What if phone numbers were thought to be too difficult for people to remember, so someone decided that all you needed was the name of the person at the bank. (Even though that name may belong to many different people across the world.) What if someone further decided that the lookup should handled by someone else. No need for you to be involved in that process. How could you be sure you were calling the intended bank employee?