Just to stir the pot, I punched the rivets out of all my drums many years ago with no ill effects at all. The lug bolts center the drum when you put it on.
Having removable drums saves a lot of time and effort when you want to get at the brakes.
Most older cars do not have riveted drums, I recall American motors cars had tapered axles and rear hubs with separate drums.
One other benefit is that instead of having four different drums that can only be used in their original position, you can move them side to side and replace them with drums from another car regardless of the side they came from.