Because Juve will still want a true CF in their squad, but Matri is the only player they have (and view as dispensable) that they can get serious cash for just now.
No-one wants to buy Krasic, but Inter have shown some sort of interest in him at some stage, so a swap (a loan swap would be more likely, I think) between Inter and Juve for Krasic and Pazzini may be the only way Krasic can be used to bring any sort of value this summer.
If Juve could sell Krasic for a decent amount, I'm sure they would do that, and keep Matri as the CF.
That doesn't seem probably just now, so what Ahmed said would seem to be the best way to manipulate things to get the best value this summer.