With their “Risk-Weights” it is the regulator who is taking the load off the books of the banks.
When the regulators used (and use) a risk-weight of only 20% to reflect the risk-weighted value on the books of banks of for instance lousily awarded mortgages to the subprime sector that manage to hustle up a triple-A rating, it was (is) the regulator who is taking 80% off the balance sheet(books)of the banks.
When the regulators used (and use) a risk-weight of only 0% to reflect the risk-weighted value on the books of banks of loans to a sovereign rated triple-A, like the US or UK, it was (is) the regulator who is taking 100% off the balance sheet(books)of the banks.
Sincerely, I doubt the banks could have managed that kind of disappearance acts on their own.