The science that is done on these telescopes is almost entirely independent of hemishphere. They look at objects so faint and far away that there are billions in view of any site.
At this price point, yeah, we should have one. The problem is that "private" scopes like Keck soak up a lot of NSF funds, having run them through the UC system, leaving less for "public" observatories like Gemini. It's using tremendous amounts of public funding to make a toy for very, very few people. It's much easier somehow to get money to build telescopes but running them seems not to be as attractive to the funding bodies.