Macrumors:

Shigeru Miyamoto has confirmed that Nintendo’s upcoming iPhone game Super Mario Run will require an always-on internet connection to play, which Miyamoto said is “a requirement that’s been built into the game to support security.” The security element is one of the big reasons why the company decided to launch on iPhone first, Miyamoto said, and it helps the game’s three separate modes function together while always keeping the software secure and safe, preventing piracy in the process.

I get why Nintendo is doing this but it makes the game less functional for a lot of people. Not everyone has a solid internet connection or unlimited data plans on their iOS devices.