Most of the unknown traffic I encounter is low (e.g. traffic circuit) so mobile reception is a non-issue. Once I am at an altitude where I do not have mobile data any more, I am on a radar or FIS frequency receiving traffic information anyways. And before I hear this argument again: I do not care about 1-2 seconds of delay due to internet, because I just want to know that there is some traffic to look out for. I do not need the exact position on my moving map.