Professor Edward Kane:

The issue is not taking risk but taking the risk of ruining the firm - the risk of ruin. People do not often make this distinction. Most firms, whatever their industry, take risks. However, people do not go out of their way to take positions that make it a really observable probability of failing. It is very unusual. Most managers want to keep their jobs and are not willing to run that risk. The only reason that managers of these too-big-to-fail institutions run these risks is they are confident they will be bailed out.