The "netting" out assumes that there are no counterparty risks which is quite plainly false.
These derivatives are all essentially bets.
That's all they are.
If there is no one to pay the bets then all the illusory and imaginary "wealth" crumbles away.
That's why bail-outs / ins have been necessary. The bankruptcy of even one of the "bookies" has follow on effects.
That's the reason why gold has had and will always have a place. For its holder there is no counterparty risk. No one needs to guarantee or warrant its worth. Rational humans have figured it out long ago.
