Saudi currency, why is noone attacking it?
Similarly to what George Soros did to the British Pound in 92.
Then the British Pound was within the European Monetary System of fluctuating exchange rates within brackets; Soros in his book Alchemy of Finance (wrote in the second half of the 80s) mentioned that this kind of system is open to a speculative attacks at the discretion of the speculator, when and where, which is exactly what he did.
The Saudi Riyal is in an even stricter monetary regime, a currency pegged to the Dollar. However, the oil price drop has weakened the Saudi economy, meaning that the forced strength of the Riyal finds no reason in reality. Very much like the Pound in 1992, the Riyal is greatly inflated by currency peg.
Should it be subject to a speculative attack, say a number of investors shorting it en masse like Soros did in 92, the only way for the Saudi central bank to support it would be to respond by being on the other side of the shorts, buy Riyals in exchange of Dollars, which can only continue until it depletes its reserves (Saudi reserves are large but they have been tanking). Alternatively, the Saudi central bank could let go the peg and take a loss like the Bank of England did and take the loss.
Sooo, why not?
Fear of revenge by terrorism?