The reasons why cats always have a little bit of poop on their butts:

1. The litter box space is too small. Cats cannot stretch out in the litter box and can easily stick to their buttocks when defecating.

2. The cat’s hair is too long. The fur of some long-haired cats is so long that it blocks the anus, so it is easy for the cat to stick feces to the fur when defecating.

3. The cat has swallowed a foreign object. If the cat swallows wool, plastic bags, or the owner's hair, it may cause constipation and cause the cat to have unclean defecation.

4. The cat’s gastrointestinal condition is not good. If the cat's diet is unreasonable, or the cat is not dewormed in time, or the cat has diarrhea due to some unclean food, it is easy for the feces to be stained on the hair.

5. The cat is too obese. Most cats will clean the poop around their anus by themselves, but some cats are too fat and cannot lick their anus, so they cannot clean themselves.