The human eye can see more than 18fps. Films are made 24fps for smoothness as with the way it projects, that's the point where it starts looking smooth. TVs (NTSC) are 29.9, and people can see the difference between that and 24fps.
Computers are 60hz and most games are 60fps. Many people notice the difference between 30fps and 60fps.
The problem I have with FPS isn't that higher is smoother, is that variable FPS can cause a bad user experience. That being said, it's the developer's responsibility to have specifications on the target hardware and scale the game down accordingly.
HOWEVER, Consoles are framerate limits due to hardware limitations and to ensure smooth operation. They're more concerned with the professional 30/60fps.
Mobile devices are also limited devices that if you can make a game run smoothly at 30fps, but have a hard time meeting 60fps, then there should be an option or a way to limit it.
That doesn't mean to not adjust the graphical load to meet hardware demand, just that framerate limiting is the /last/ step you do.
IMO while there is justification for a FPS limiter, there's no real reason to do so while the market and standards are changing so fast your game might run at 30fps today, but 60fps next week.
Once the field settles, and limitations are being met left and right, then maybe there would be a real reason. (Although a global delta-time multiplier to enforce framerate shouldn't be too hard to implement)
Edit: But this is mostly PC/Browser games. Mobile exports are usually 3rd party so it would be an option for CocoonJS or Phonegap to introduce FR limits to set for apps.