Get off the plane in a developing country. Some of those airports are not nice. Some of them are nice shells that are almost deserted, with no wifi and a couple vendors that won't take your American credit card. Your "World Plan" often works, sorta, but you can't always get data due to different radio bands or because the network is simply not good enough for a 100+mb download.
You'll either have to hop into a hopefully licensed taxi, or start walking in the dark in an industrial area (where airports usually are) in order to find a wifi hotspot or a street vendor that will sell you a SIM card.
It's not fun.
Uber made the right choice.