Considering you can get to pretty much every other major city on earth from JFK and LHR already, I dont see where these new markets are.
Climb 150 - the important part you missed is some key benefits around payload and cabin mix. The longer-range bird will improve both these
very crucial elements of route profitability. Why wouldn’t I serve a market with equipment that enables a larger uplift of payload or a better mix of cabin configuration, and achieve the range I need to leverage the point-to-point advantage - in particular on thin routes. Every cent counts where the market is saturated with competition too. So whilst existing metal can achieve most of the destination mix you refer to - they do in some circumstances carry restrictions that could be mitigated, and even exploited with metal that can deliver the distance with the
desired payload and mix...