I'd REALLY love to hear an explanation for this from SE. In my experience (and pretty much all answers in this thread so far seem to be of the same opinion) players enjoy that last remain of actual exploration.
I loved doing it, and I know no one who was even remotely annoyed by it, everyone considered it a natural/fun part of being new to an area.

I know you want to make things easy for new players so they can catch up faster, but unhiding the maps instantly does not speed up their progress in any way, since important parts like aetherytes and dungeons and the like were visible before already anyway. All this is doing is destroying the experience for those who enjoyed wandering off into every nook and cranny to see everything and then be rewarded with a bit of exp and an achievement.
Please change it back. This was more than uncalled for.