Your cats smell is 100 times better than the human nose.
Many guardians complain about cats not using the Litterbox and can’t understand why.
Though there are SO many reasons your cat may choose to stop using hte litter box, one of the most common is the smell.
You may not be able to smell the box, but they can, especially when they are so close to it, and especially when they are digging in it.

Even if your cat is great about using the litter box, for their sake keep it cleaner than you think it should be. And if you want to prevent future litter box issues, keep it cleaner than you think it should be. AND, if you are having litter box issues, keep it cleaner than you think it should be.
This also goes for scented litter! Some of the scented litter is too strong for their sense of smell so they refuse to use the box. Unscented litter that is cleaned at least daily is the best option for most cats (and their sense of smell).