If the bank employee takes an action that forces the bank to book a loss this year, on a loan where the book loss could have been postponed 10 or 15 years, the bank's management and colleagues' reaction is going to be: "you asshole". Add to that banks being highly leveraged (they carry only 2-7% reserves, depending on their line of business and quality of their portfolio), just one loan going declarably bad can trigger a lot of regulatory scrutiny and possible close examination of their remaining loans carried at book value. (see prior comment about bank runs)