It's not just about games. With the proliferation of smartphones, kindles, etc. It really comes down to what would I rather do with my idle time? Instead of paying for a 3DS or Vita, I can read a book; watch netflix (yes, I know you can do that on the 3DS, but thats not a differentiator); play a cheaper game; or surf the web (see netflix comment above). That's why smartphones are going to kill the 3DS and Vita - it is easier/cheaper to waste time on them.