Voice calls are a slightly more "secure" alternative to text messaging. It's more resource intensive to store and analyse audio/video than text, and less accura

Voice calls are a slightly more "secure" alternative to text messaging. It's more resource intensive to store and analyse audio/video than text, and less accurate to boot. It's easier to run `SELECT * FROM messages where messages.body LIKE '%tiananmen square%'` than it is to run speech-to-text over bulk data and run the same search. Obviously that's a trivial example, but digital text (i.e. not handwritten) is always going to be easier to parse than speech.