They have no reason to unless you default under your debt repayment obligation....if you havent defaulted they will not ask you to reduce your principle or loan amount.
You see there are many reasons fo this....without me writing a 4 page essay.....the more cash the bank has out the bigger roi.......if the values all went down the banks would have to readjust every loan they have on their books and it would interfere with their internal policy when it comes to sale of a loan book, credit rating, et etc......Most loans after 2 years are sold off as a loan book so even though u may have a CBA loan managed by the CBA ....odds are the loan has been sold off to some super fund or other securitised group.
