It actually does add value in this case. It makes it impossible for governments to shut the market down because it's decentralized (Unlike Intrade which was shut down). Also, anyone in the world can participate, even people with no access the financial system or a government ID.

Actually from what I can tell, it is a more liquid model.

In Augur you buy shares of an outcome, and the value of those shares can change day to day, and you can sell at any time. Whereas with a bookie, you bet on the outcome with fixed odds. Bookie lines may shift, but your bet will be locked in and unable to appreciate in value.

I'm not sure why bookies haven't implemented this share model, maybe its needlessly complicated.

Bookies have implemented this. Betting exchanges have existed for over a decade now, you can lay off your bets to lock in a profit if the odds have moved. Even 'traditional' bookies offer various forms of cashing out a bet.

Could you name some of these exchanges? One problem is that they may not service certain jurisdictions as well.

Betfair is the biggest one.

You are misinformed, at least in this case.