GSP specifically asked for Diaz.
This should really be the end of the thread. GSP asked for it. Does anything else matter at all considering how reasonable the request is? GSP isn't asking for Serra - GSP 3.
Because the UFC prefers to milk people rather then putting on fights which should be taking place instead.
If you, like many fans, believe Diaz won the fight vs Condit, then this fight is the fight "which should be taking place".