 Why would someone endorse the existence of absolute time? One reason is that the empty container metaphor has a lot of intuitive appeal. Another reason is that some philosophers have thought that there must be such a thing as absolute motion—as opposed to merely relative motion—in order to explain certain physical phenomena, like the forces felt during acceleration. Newton had an especially famous argument along these lines involving a spinning bucket of water—the entry on  Newton’s views on space, time,  and motion has a careful discussion of this argument.