Maybe it's moral.
If all else is equal, maybe the banks don't want the borrower to escape punishment?
If you gag on using the words "moral" and "bank" in the same sentence, how about "precedent"? As in, not establishing a precedent that you can walk away from a bank loan unscathed.
Just flashed on ER's recent anecdote about borrowing money from a loan shark. The dynamics are same, regardless of who's doing the lending. Only difference I can see is the cut of the suit.