[spayu61]

I believe the difference is intent--a phone call self destructs by default. They are not meant to be recorded (we even have laws here that prohibit it without consent of both parts). Messaging apps have, traditionally, kept logs, in both ends and in the server.

[ISL]

Entirely agreed, though it is true that intentionally-private messaging apps have, traditionally, not kept logs. That's a tradition worth keeping!