A theory. Shoot it down if you wish.
Restaurants like Noma appeal to a very small number of people who are interested, willing and able to pay their prices. Usually as a one-off, I'd guess. How many repeat customers fo they really get? I'd bet on few to zero. They arent picking up walk-ins, that's for sure.
So once they work through that tiny clientele where else can they go? Bust? Or do something else? Same as El Bulli.