Handhelds need to have some sort of phone functionality a la calls and texting. Most people don't have to carry around multiple devices and its much more convenient to have everything in one place. iPhones and Android satisfy that notion and most people already have them. That leaves mainly the kids for handhelds and parents aren't exactly rushing out to buying their brats $250-$300 on handhelds plus paying for memory sticks and games
The main issue here is publishers/developers thinking its okay to release a broken game and then promise to fix it once everyone has bought it and suffered through playing an unfinished game
BPoole96's comments