Individual countries won't want to pay what amounts to a tax for going it alone. Airplane companies are expert at producing futuristic drawings, sometimes like the vaporware that software developers generate to discourage competition. Yet, as Kirkland points out, if the next airlifter has to be multi-company and multinational, it's time to start the concept process. And a company has to be prepared to answer quickly if a customer suddenly asks. Thus, user concerns like C-17 vortex problems in air drops or ease of loadability got overlooked.
Nobody likes playing logistics wargames.
They are just not sexy.