I'm amazed at the frankly moronic comments here.
Cats are 'dirty vermin'; really? Burying their poo? How many animals do that? Mink **** where they sleep - now that's dirty. Dogs take a dump whereever they feel like it and **** all over cars, trees, anything that is stationary - that's dirty.
None of the cat scat left in my garden is buried - unless you count a shallow depression as burying.