Hubs work best where there is a base of O&D traffic, but that's not the whole of the hib's traffic. EK can't exist only on DX O&D, neither can DL live off of ATL or AA of DFW traffic. But, there's enough and its "catchment" area is huge. If you're in North America and traveling to much of Africa, India, the ME and even parts of SEA, EK thru DXB is the very good option which is why it does so well. That's why they can attract so much premium travelers. The "bar car" biz lounge on the 380 typically has an amazing crowd of premium travelers.

Does the "open skies" agreement allow US carriers beyond rights?

GF