Or, the other way of saying is why are there few replacement chainrings for shimano 92mm?
No triple available in dura-ace, triple in ultergra is 92mm so can't replace chainring. Only option is to drop to 105 crankset. SRAM/truva... only offers 9 speed, i.e. "mountain", all roads are doubles only. Campy has very neat 11 speed 12-27, but it only works with doubles. For triple have to drop back to 10 speed cassette.
Did someone flatten the hills over the last year or so?