Because Cassano would come on the cheap, especially compared to Diego.
Don't get me wrong, Diego is a great player, but Cassano BELONGS in Serie A.
People forget he's only 25 years old. He just needed to be in the right situation.
Sometimes people forget that when he is in the right enviroment, surrounded by the right people (E.g. The Italian National Team during Euro 2004), he is not only a great player, but a model citizen and quite humble.
If they can get him at a reasonable price, with true champions like Alex, Pavel, and Gigi here, then it would be a terrific buy.
Personally, I'm all for it.