It's Hearts of Iron...what on earth kind of diplomatic bargaining could you possibly do? Nor do we care about suspense, we care about game play.
France: Psss...Italy...if you join our side, you get Tirol and Croatia!
Austria: Psss...Italy...if you join our side, you get some French colonies, Nice and Monaco! Enjoy gambling your taxpayers' money away!
Italy then decides who has the better offer and joins whichever side looks more likely to win. Remember Napoleon's comment that any war involving Italians usually ends with them on the opposite side.
There is a lot more "game play" for France or Austria to worry about if Italy could suddenly backstab them and invade. Have you ever played Diplomacy?