They prefer a win-win situation a short sale offers. The lender knows that they are losing money and expect to suffer a lost. They just want to minimize that loss as much as possible. A recent study showed that a short sale reduces a lender's losses by 20 percent. In my experience with short sales, that number has been much larger.
A seller’s job is to be friendly and open with the lender so that the lender is more comfortable with the option of allowing a short sale. Sellers should be prepared to write a good hardship letter, and provide the lender with all the important documents so that the lender understands the seller’s situation. That way the lender may even help the seller throughout the procedure by looking for an agent that could help him, etc. The seller is not required to argue with the lender or be hostile. Sellers should keep their egos aside when dealing with lenders. An aggressive and hostile approach is not needed.