In the "NA Siege is dying" thread, posts suggest that an alternate map rotation was proposed and submitted in the appropriate fashion, but for some reason the server admins/devs (not sure which exactly) decided to implement EU's map rotation instead of the improved line-up.
That same thread makes it clear that a majority of players are sick of the maps that are being hosted, and would prefer that new maps, and maps from the "ATS days" be used. There are more than enough siege maps from those two categories for the server to have a completely new rotation. The lack of any feedback from the devs on the matter makes it look like they just don't care about the preferences of the players.