i can't tell you why a "non designer" would like an AA poster, because i'm a designer.
but, i can assure you that AA has a strong visual connection with the music, fans and "scene" for lack of a better word, that they deal with.
their fans respond to their posters the same way a dirthead kid in the early 90s would have responded to Dio's "Holy Diver" album cover. they connect with it, they love it, it represents them and their peers.
while i don't really connect with all of the music AA does work for, i like almost everything they do.