I guess they think it's easier to find 3B than 2B.
Besides, even though Izturis doesn't have the range that Lawrie has at 3B, his defense is smarter and more mature so it's not a big down over Lawrie, at least for now.
It's also pretty clear who they want to keep out of Derosa, Kawasaki, Bonifacio and Izturis, obviously he's the only one who can hit on some level of consistency.