Touchscreen violence, why are developers wary of exploiting its full potential?

Edge – "This month I have mainly been shooting vast quantities of men in the face. That would make it a perfectly ordinary month were it not for the fact that I’ve been doing so on two portable electronic devices that a decade ago would have seemed like futuristic sci-fi mockups for a high-budget movie. The contrast between the two games is instructive – the one that is a really good face-shooter, Killzone: Mercenary on Vita, is a summing-up of the past, while the one that’s less satisfying, Call Of Duty: Strike Team on iPad, has more to say about the future."