If you Google for information on it, it's a bit of a mystery... I know one person who says they have to Tellurides, built 1 month apart and one has the menu item the other doesn't. I've seen people claim that it's somwhow related to the trim level you have, but that seems debunked as well.
On page 4-77 of my owners manual, it says this... "To use the service interval menu, consult and authorized Kia dealer."
To me, that basically says Kia has to enable that feature. However, in my Google searchs , people have claimed they have gone to their dealers and they have been told they know nothing about it.
I guess I should contact my dealer and find out what they have to say. But then, I more or less made up my mind, that the default 7500 mile interval was actually not a bad thing. I plan on changing my oil every 5,000 miles, but if should get busy, I wouldn't be concerned about occasionally going out to 7,500 miles, so I view the 7,500 mile interval as a backup reminder to change my oil.