Before you judge me, it's not because it's great design or adds to gaming in anyway, it's actually the opposite of that. The touchpad is such a specific thing to the vita, it can't be copied by anything else, meaning emulation is completely impossible for any game that uses the back touch pad. Touchscreen gaming is different because a mouse can substitute for the touchscreen. Yes, a mouse can substitute for the back touchpad, but they're meant to be used in unison, on the fly, so it would be wanky flipping back and forth between using the touch pad and the touch screen with a mouse.
And yes, I know this was probably unintentional, but it still works out well for sony
Honestly, it probably doesn't matter either way, because the vita has been a shit show (sales wise) for sony.
Maybe there could be a workaround? I'd appreciate some theories