Why do animals have to eat rotten food, instead of cooked food?

Animals haven't the ability to cook food, but they have a special set of acids and enzymes in their digestive system, and also have a strong immune system in order to process the bacteria present in the raw meat.

Our ecosystem also needs these type of animals which are grouped as scavengers and decomposers.

They are most important to us because they prevent waste and the remains of dead organisms from being piled up, and release the nutrients back to the ecosystem from the waste and dead organisms.

They also prevent the spreading of diseases, born from rotten plants & animals.

That's why there are some animals who eat rotten meat.