At the recent general shareholders meeting, Nintendo revealed that the company had the resources to develop their very own smartphone peripherals, and would actually consider making smartphone controllers if they felt it was the right business decision.
According to Shinya Takahashi, the general manager of entertaining planning and development,
“Physical controllers for smart device applications are available in the market and it is possible that we may also develop something new by ourselves. On the other hand, I believe Nintendo’s way of thinking is to look at whether action games are really not impossible (without a physical controller for smart device applications) to create and how we can make it happen to create such a game. I think we will make applications, and not just action games, in consideration of what best embodies ‘Nintendo-like’ applications, including applications for everyone from children to seniors.”
Of course, a lot of mobile games work perfectly fine without controllers, and they play well with just a touchscreen. However, platforming games and other RPGs might do well with controllers, as simply tapping virtual buttons on a touchscreen could cause players to lose some precision in their gameplay. Not to mention, controllers would reduce clutter on the screen, greatly improving the experience of playing games on your mobile phones.