In theory pet food shouldn't be bad for people to eat per se, but in actuality the ingredients and processing are not regulated in the same way and may not be suitable for human consumption. It is inferior in quality and safety standards compared to food that is, therfore, it is more likely that it may contain something harmful.
Animals like chinchillas live only a fraction of our lifetime so ingredients that may cause cancer or have long term effects can be used in animal diets that cannot be used in human diets.
Raw loose hay should probably not be consumed since the way it is stored and dried may invite the growth of microbes that we are not used to consuming and may not be immune to. These can be introduced by rats and insects. We do not store and process people food the same way for our diets.
