What do you mean? The persons that i know is still using phone numbers to contact, in fact, at some remote places people had no choice but to buy a phone number to get into Internet.

And how the hell do you memorize these randomized strings:

347a2370900d19b4e4756221594e8bda706ae5c785de09e59e4605f91a03f49c

Even it's possible, Only a few people will do it. In fact, There's no way that people want to retype that long string into a phone again.

People still prefer to reach via the existing platform because "the function still works well. so what's the point of switching?". Even you told them about the privacy, These people will instead says "you are being paranoid" and that's it.