This link has faqs which bring out the fact that why whistleblowing is important even if you are not a party to unethical practices.
But there are many broader issues which make an honest person to become a whistleblower. Most important of all is not being able to keep quiet and become a silent partner in unethical practices that too when doing so could mean killing innocent people and in particular the poorest in the society.Corruption is the tax paid by the poorest is not understood by many. The fact that corruption kills is some thing even not many want to understand or ignore if told as they do not see themselves directly responsible. It is similar to a firing squad in which each person feels that he shot a blank and is not responsible for the killing and that another person's bullet killed the guilty. But corruption is worse than such firing , as the corrupt indulge in the murder of innocent poor defenseless people. Child mortality, pregnant mother mortality , life span of the poor all show that corruption does more than keeping the poorest very poor.