The reasoning for including them is that they had a presence ranging from the Aleutian islands in Alaska to Baja California as raiders. With as interesting as their culture is and how notable the Pacific Northwest is for its distinctive artwork, they’d lend themselves as an excellent campaign-useful civ as well as just being wide-ranging for any other campaigns that occur anywhere between Alaska and Baja California.
They have stories of raiding Hawaii. They were prominent in the Pacific Northwest, and they’re only one piece of the Potlatch gov’t system I lightly touch on here - otherwise, the other Potlatch tribes would have stretched from southern Alaska to northern California, and quite a ways inland.
I just chose the Haida specifically for the emphasis they have on raiding and their unique style of boat.