Because that’s how they learned to do it from their mother. Burying its feces is instinctual in cats, but the way of doing it is learned. Many kittens never see their mother bury her feces, since the mother must use a litter box with a lid or where she is hidden. It is possible that, since the kittens did not see their mother scratching, they did not learn how to do it properly. The LitterBox by LitterLocker, which does not have a dome, allows this essential learning.