OK, obscure, maybe not, but low population, for sure.
Yes, I believe that U2 could sell-out a show in New Zealand and Australia, probably quite a few shows, but are they supposed to ship all that equipment and people just for a handful of shows. They would lose a ton of money.
Yes, Ireland may get the concerts, as well as Portugal, Norway, and many other countries comparable to or with less population and attendance than Australia, but all those other places are not off by themselves in a remote part of the world. Australia may be their most dedicated audience, but there's not enough people. Fargo, North Dakota could have the most dedicated audience in the world, but I know U2 is not going to play a show there and it's within a days drive of Minneapolis.