Indeed, this is the main reason I'm using Signal (and badgering my friends into using it). I want to increase the volume of encrypted non-sensitive stuff, so that the "list" doesn't have predictive value.
Having metadata (i.e. who communicates with who at which time etc.) still has lots of value for the three-letter agencies (some even say it's even more important then the content of the messages itself). As far as I know Signal does nothing to avoid this kind of metadata (but please correct me if I'm wrong).
