Telephone numbers are just meant to be somewhat organized line noise. Humans can just treat it as a big arbitrary blob of data they have to type in. But domain names are meant to be "human readable" but just look at the mess the URL makes of them?

Phone numbers were that way because telephone companies had to organize a hierarchical set of wires that could make physical connections between any two endpoints with limited relay-driven processing. Packet switched networks are supposed to abstract away topological addressing for the higher layers. Why make users type it in? Why, with all of the computing power we have available, do we make users put in the protocol? Protocol is certainly not relevant to most users. I've even known CIOs to mess that one up. Why put it in front of them at all for the default situation?