Good point Larry.
Most "newer" systems are running stereo. The digital boards have the benefit of having most effects, compressors, gates, etc on-board...it's not difficult to run a GOOD stereo mix.
It's often the "OLDER" systems and forgive me, older engineers, that try to get away with mono these days. Guys who haven't upgraded their systems or their thinking.
That said, traveling internationally I have had NO issues. Although being in a 2 guitar band, we do try to make things easier sometimes, especially if there is a language/communication issue. We don't ALWAYS have a FOH engineer with us, so it is what it is.