Playing devil's advocate here but phone doesn't have a unique official logo. People use what they prefer yet everybody gets it.
Discussion
Nobody is talking about unique official logos here
Yes, but we have phone numbers. Phones have been around long enough that you don't need to draw a picture of a phone next to a phone number for people to understand it. That isn't true for a public key for most people. Some keys can look similar and provide little context as to what they are for. For example, my username on most social was @mattkwarren. Cool. Where? Most people will recognize the Bitcoin logo more easily than a Bitcoin address. Yet Bitcoin is also a protocol.