Because this game used to put a lot of care into crafting its setting and new characters within those worlds. The omenpaths arc has opened the door for wotc to do what feels like much lazier work on that front by recycling old characters and having them do "gimmick of the week"
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They had a whole process to chose the sets that where a part of it between design and creative, and the Lore and story is good.
And Amonkhet got chosen specifically because it didn't have any sets mapped out for the future, didn't require too extensive worldbuilding to adjust to modern standards and hadn't gotten any revisits.