Oversimplified answer: because people want their cellphone to work outside of major US cities.
For example, the laws on what is allowed to use encryption and what is not differ significantly from country to country. There are also often older installations that only provide 3G support.
Basically, it's complicated and there are a lot of different reasons but it mostly comes down to the world being a big place with lots of different laws and requirements, yet people want a phone that works everywhere.
For example, the laws on what is allowed to use encryption and what is not differ significantly from country to country. There are also often older installations that only provide 3G support.
Basically, it's complicated and there are a lot of different reasons but it mostly comes down to the world being a big place with lots of different laws and requirements, yet people want a phone that works everywhere.