Well after the Type-0 announcement I guess we know why. The Vita in a america is done. SCEA has no intention of making any content for it. I mean damn, Soul Sacrifice Delta was localized by SCEJ.
I don't think I've ever seen a situation similar to the one the Vita is in. Its platform holder's main division has dropped it without ever even supporting it.
SCEA refuses to show off the games it even does have. They haven't tried with the device since 2012. For all intent and purposes, the Vita was dead to SCEA by the end of 2012.