If you think that this is happening due to the fact that your cat is very clean, then we hasten to disappoint you. Cats, of course, are still clean, but that’s not why they bury their waste. In fact, an instinct speaks in them, which they inherited from their wild ancestors.
Undomesticated cats living in nature knew that the litter - this is the most easily detectable trace by which predators could understand who left it and how long ago. That is why wild cats covered their tracks so that they could not be found, and also could not find out any information about them. - male or female, sick or healthy, etc.
And although domestic cats do not need to hide from predators now, instinct still leads them to bury their waste.
The same instinct, by the way, sometimes drives cats to start burying their food in the bowl. If you notice this behavior of a pet, then this does not mean at all that he mixed up the bowl with the tray or hints to you that the food is tasteless, - this is actually how your cat tries to hide its prey from others.