Originally Posted by
xliioper
I suspect because at the time they went revenue-based earn, everyone else was pretty much still mileage-based and it would be difficult to earn more than 75K in a trip in most other programs at the time and thus they did not see going over 75K as a significant competitive advantage. Circumference of earth = 25K miles + 25K class of service bonus + 25K elite bonus = 75K miles.
This all predates my enlightenment out of kettle-dom, but when they went revenue-based, was the award chart still fixed? If so I'd think that had something to do with it too, i.e. maybe they didn't want you to be able to just mint an arbitrary number of free trips by buying one single expensive ticket.