It could be a graphic intensive title as it is considered an 'optimization mission' for them to port to vita.
http://thevitalounge.net/double-eleven-adapting-ps3-title-for-vita/
read line:
“Our next title sees another PS3 title being adapted & improved for VITA.Starting at 3fps its an optimization mission to get up to a solid 30″
Sign this petition please if you want GTA san andreas on PS Vita:
http://www.change.org/petitions/rockstar-games-port-grand-theft-auto-san-andreas-to-the-playstation-vita
And please spread it to various sites/forums etc.
Upcoming notable indies for PS Vita:







