There's yet another block some might encounter A a, for example, has to be able to see a through fare on the main / transoceanic carrier from one's origin to destination (not a "married" itinerary), and something like SAT-GPS is just not likely to exist.

With Galápagos, most ultimately fly an award into UIO or GYE and buy a trip to the islands (often with their trip supplier, most often on a flight booked for a group), as going to the islands on a whim is not likely to be rewarding).