Body oils pheromone scent and not to mention their disease infested urine and droppings are all things left behind by rats. These scents and droppings left behind by rats can attract future rodents. Clean attics will deter future rats and save your health. As you well know rats carry many infectious diseases. And further more urinate and leave droppings that are prone to develop fungus aerosolized viruses. The unsanitary conditions that rats leave may pose a threat to you and your family's health. Special care must be taken when dealing with rat urine and feces. Gloves, respirators, and biohazard suits must be worn when handling rat waste to prevent contamination. Then the property can be sanitized and deodorized.
1) Animal waste is a biohazzard - leaving droppings in the attic long term can have health consequences.
2) Animal waste attracts other animals. Future animals will scent the attic and try to reach the prior animals.
3) Leaving droppings in the attic is particularly unattractive to new home buyers.
4) Some customers continue to smell the waste inside the home and the odor needs to be dealt with at its source, not by masking agents in the home.