They probably switched to the Kilimajaro/JC hats because the white gambler hats they used to use were expensive and didn't last very long. We also didn't have very many. I remember one day at DAK costuming we got in 20 of them, and they were gone by the end of the next day. And then when they come back they were always crushed and stained and whatnot. Kilimanjaro hats worked much better and had a longer life.
That's me defending the hats....
I don't really care for these new costumes all that much. They're kind of bland compared to the old ones.... And I have an immense hatred of khaki pants, but that's just me.