Why do animals live to be 20 years old eating crappy food??
The same reason some people can live for many, many years and smoke, drink, and eat junk food. I had an old lady who lived down the street from me growing up who lived to be 97 years old. She refused to ever go to the doctor, smoked 2 packs a day, drank hard liquor every day, and seemed to eat mostly cookies and stuff out of cans. My grandmother, on the other hand, ate well, exercised, never smoked a single cigarette, rarely drank, had regular doctor’s visits, and died at the age of 72. Some people, and animals, just have better genetics, allowing them to live longer, even if they eat junk. Imagine how long those cats would have lived if they ate good food!