The difference is if someone sets fire to a factory that fire will be investigated and odds are that person will be caught (not always, but few people know how to set a fire that large and cover their tracks). By contracts someone who works in the factory is much more likely to be able to figure out how to "have an accident" doing something they normally do, everyone knows it is then but they just get a "do better next time" talking to, and the factory throws up some more guards.