Why don't animals have to have good hygiene?

Humans have "good hygiene" based on a concept that can have very little to do with

health/ sensible cleanliness. Many human "hygiene" practices, daily bathing, sanitizing, disinfecting, constant hand washing that dries out the skin, etc can actually be detrimental to health and can diminish the function of the immune system.

The definition of hygiene is the practices/methods used to preserve good health.

Animals practice hygienic behavior all the time unless of course people confine them

to an artificial environment that is unclean, stressful or neglectful.

Wild animals are adapted to the environment they live in...it is only the human idea of "hygiene" that makes an animal seem like they don't have good hygiene.