An alternative question would be, “Why do domestic cats paw around their food?” The reason why they do this is because there is no earth (soil) to paw at therefore they paw at the hard surface of the kitchen floor. But what is the underlying reason for this behaviour?
My cat did the exact same thing this morning. I gave him a very nice meal of wet cat food. It is high quality and he normally eats it quite quickly. I know that he enjoys this brand of cat food. This morning he ate half of it and then tried to bury the remaining half. About three or four hours later he came back and ate all of the food that he had tried to bury and the entirety of another bowl. So what does this tell you about a domestic cat trying to bury their food?
Well, it tells me quite clearly that if my cat rejects food and then tries to bury it he lacked sufficient appetite at that moment to eat it and is burying the remainder of the food to protect it from beind scavenged by competing predators. In burying food they remove its scent. He can come back to it later on and finish the meal then. This mirrors what happens in the wild. I’m particularly drawn to thinking about the mountain lion (puma, cougar). This magnificent large wild cat species likes to bury prey animals in leaves.
On one occasion a puma buried a man who was sleeping in the open! Don’t sleep in the open air in mountain lion territory unless you know what you doing! I can say with certainty that it normally not a matter of a cat disliking the food when they paw at the ground around the food. It is an instinctive response to burying it which is exactly what it looks like. Sometimes, it will be a rejection of the food but this is obviously linked to a lack of appetite at that time and the same underlying reasons for pawing at the food bowl apply.
As a postscript, you see the same sort of behavior occurring in cat litter boxes. When a domestic cat tries to bury their poop in an enclosed cat litter box they sometimes scratch the sidewalls as they try to scrape what should be soil over the poop. They don’t understand it and sometimes continue to scrape against the plastic walls of the litter tray without success. On this occasion is about hiding the scent of the poop which may in part be due to submissive behaviour. I think you will find this happening in feral cat colonies sometimes when a submissive individual does not want to stand out and antagonise a more dominant individual. It’s a bit like hiding physically but in this instance it is hiding the smell.