[ghaff]

Yeah. A lot of it is convention of course. But where I work, Google Chat for individuals and small groups has sort of developed in general into a higher priority interrupt than email. e.g. are you joining this scheduled call?

On the other hand, the group chat for a broader team I'm in is more likely to be used for idle non-work-related chit chat.

And phone calls basically aren't used at all outside of scheduled meetings.