The old 50 (Hard) dungeons were Expert dungeons during the patch they came out. For example in patch 2.5 the Expert roulette was Keeper of the Lake, Wanderer's Palace (Hard) and Amdapor Keep (Hard). They got pushed into High Level Roulette (renamed 50 roulette in HW and then 50/60 roulette in SB) once the next set of Experts was released.
Between that and the relic grind a lot of long term players are probably sick of every old level cap dungeon in the game.