Banks needs to be forced to sell these things because what happens if they accept an offer like this is that they actually “loose” money since it’s collateral for other things at a certain value. This starts a downward going spiral that makes the banks go banrupt… not that it should though. It’s all about fake values in the banks portfolio and how they can get away with it.
If you study the reserve ratio demands you will find that in reality a bank actually makes a better deal to keep these sort of portfolios since it’s so easy to fiddle with their values. This means have cheaper costs for other loans. Indirectly these costs are carried by the rest of the banks customers and in the end the tax payers.