[yorwba]

> How does WeChat satisfy something very long-term like that?

You can search your message history. I think that's enough for most personal archives. Of course if WeChat goes away, many people will be unable to access their archives, but at the moment, few seem to be worrying about that.

> Being mobile savvy has nothing to do with it.

Not being internet savvy before becoming mobile savvy has something to do with it. I'd wager that most heavy email users had an email address before they got their smart phone.

If you don't already have an extensive email archive, keeping all your personal communication in email no longer seems so compelling.