Smelly cat food

If we judge cat food to be smelly we have to remind ourselves that it might not be smelly from the cat’s perspective. Food is designed to smell attractive to cats obviously. A lot of people say that cat food has an unpleasant smell but they are judging it from a human perspective unless they are talking about wet cat food which has been in the bowl for more than an hour or so. In this case it does smell absolutely horrible. The big question is why wet cat food goes off so quickly in terms of smell. It looks all right after one hour but it smells disgusting. Is this due to the chemicals in the food or drugs in the food imported through raw ingredients which contain example euthanasia drugs or pesticides?