The problem is the longer the route, the larger the effect of the compounding nature of fuel burn as flight time increases. If you look at something like PER-LHR the B787 is around 575 Kg additional fuel burn per ton of payload (16:30 flight time) compared with 385Kg per ton and a BNE-LAX (12:00 hour flight time).
The simple economics of it is that comparing a single sector direct will always have a higher burn overall burn compared to a one stop near the mid point.
The counter point is higher maintenance costs, landing charges & pax handling charges by transiting at a stopover/hub. A hub also allows airlines to increase yield and utilisation of their network.
Routes that work well for ULH point-to-point are probably going to be a more expensive operation for an airline given the fuel vs intermediate stopover tradeoff, for which they are going to have to charge a premium. The best premium comes from a significant time reduction between two points Other airlines operating similar aircraft but with a low cost hub are likely to be able to have a lower cost base, at the expense of travel time.
In my understanding of the world, suitable city pairs for ULH are ones where a direct flight significantly reduces travel time between two cities of significance, generally financial & business centres. Airlines using the intermediate one stop model will be able to capture the non time sensitive travel at a lower cost base using similar equipment. How much of a market is there for these city pairs for Boeing & Airbus, it probably isn't likely to be an enormous market for them.